Conjugated Polymers and Their Use in Optoelectronic Devices

ABSTRACT

Disclosed are certain polymeric compounds and their use as organic semiconductors in organic and hybrid optical, optoelectronic, and/or electronic devices such as photovoltaic cells, light emitting diodes, light emitting transistors, and field effect transistors. The disclosed compounds can provide improved device performance, for example, as measured by power conversion efficiency, fill factor, open circuit voltage, field-effect mobility, on/off current ratios, and/or air stability when used in photovoltaic cells or transistors. The disclosed compounds can have good solubility in common solvents enabling device fabrication via solution processes.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/785,357, filed on May 21, 2010, which claims priority to and thebenefit of U.S. Provisional Patent Application Ser. No. 61/180,256,filed on May 21, 2009, and U.S. Provisional Patent Application Ser. No.61/323,152, filed on Apr. 12, 2010, the disclosure of each of which isincorporated by reference herein in its entirety.

BACKGROUND

A new generation of optoelectronic devices such as organic photovoltaics(OPVs) and organic light-emitting transistors (OLETs) are fabricatedusing organic semiconductors as their active components. To becommercially relevant, these organic semiconductor-based devices shouldbe processable in a cost-effective manner.

Bulk heterojunction (BHJ) solar cells commonly are considered the mostpromising OPV structures because they can be fabricated usingroll-to-roll and large-scale production. BHJ solar cells include aphotoactive layer disposed between an anode and a cathode, where thephotoactive layer is composed of a blend film including a “donor”material and an “acceptor” material. FIG. 1 illustrates a representativeBHJ organic solar cell structure.

State-of-the-art BHJ solar cells use fullerene-based compounds as theacceptor material. Typical fullerenes include C60 or C70 “bucky ball”compounds functionalized with solubilizing side chains, such as C60[6,6]-phenyl-C61-butyric acid methyl ester (C₆₀PCBM) or C₇₀PCBM. Themost common donor material used in BHJ solar cells ispoly(3-hexylthiophene) (P3HT).

Important performance parameters for BHJ solar cells include powerconversion efficiency (PCE), open circuit voltage (V_(oc)), fill factor(FF), and short circuit current (J_(sc)). PCE (η) can be determined bythe equation:

η=P _(m)/(E*A _(c))

where P_(m) represents the maximum power point of the solar cell, Erepresents the input light irradiance (measured in W/m²) under standardtest conditions, and A_(c) represents the surface area of the solar cell(measured in m²). Because FF is defined as the ratio of the actualmaximum obtainable power, (P_(m)) to the theoretical (not actuallyobtainable) power, (J_(sc)*V_(oc)), or simply FF=P_(m)/(J_(sc)*V_(oc)),it can be seen that PCE (η) is directly correlated to each of V_(oc),FF, and J_(sc):

η=P _(m)/(E*A _(c))=FF*P _(sc) *V _(oc))/(E*A _(c))

In addition, one of the fundamental limitations of solar cell efficiencyis the band-gap of the donor material from which the solar cell is made.A common approach to estimate the band-gap of a π-conjugated material isto measure the optical absorption and calculate the energy at thelongest wavelength onset. It is generally believed that, in order forBHJ solar cells to be commercially viable, they must achieve high V_(oc)(>˜0.7 V), high FF (>˜65%), and an optimized J_(sc). It has been shownthat J_(sc) is optimally satisfied by absorbers having a band gap <˜1.6eV.

It is important to point out that the V_(oc) of a BHJ solar cell can bedetermined empirically by the equation:

V _(oc)=−(E _(HOMO)(donor)−E _(LUMO)(acceptor)+0.4)/e

where E_(HOMO), E_(LUMO), and e are the Highest Occupied MolecularOrbital (HOMO) energy (or HOMO level), the Lowest Unoccupied MolecularOrbital (LUMO) energy (or LUMO level), and the electron charge,respectively. For example, the LUMO level of PCBM is about −4.3 eV. TheV_(oc) of a solar cell, therefore, also can be used to estimate the HOMOlevel of the donor material (given the known LUMO level of PCBM). TheHOMO level of the donor material often determines its air stability. Forexample, state-of-the-art P3HT/PCBM BHJ solar cells typically have aV_(oc) of about 0.6 V, suggesting that the HOMO level of P3HT is ˜5.3eV. However, it is well known that P3HT has poor air stability. It isgenerally believed that a donor material having a lower HOMO value thanP3HT (i.e., ˜5.4 eV or lower) will have improved oxidative stabilityover P3HT. In addition, as explained above, a donor material with alower HOMO level also will likely increase the V_(oc) of a solar cell,and in turn, its efficiency.

State-of-the-art BHJ solar cells (e.g., P3HT/PCBM-based solar cells)exhibit a PCE of ˜4-5%. However, they have several fundamentallimitations. First, the band-gap of P3HT is ˜2.0 eV, and it can absorbonly a small portion (30%) of the solar spectrum. It is important todevelop a donor material with a band-gap of about 1.6 eV or smaller sothat a larger portion of the solar spectrum can be utilized. In otherwords, the donor material needs to have an absorption onset at ˜800 nmor larger (the absorption onset of a material is equal to 1240 nmdivided by its band-gap) to match the peak intensity region (700-800 nm)of the solar spectrum.

Accordingly, much effort has been made to develop low band-gap (<˜1.6eV) donor materials to replace P3HT in BHJ solar cells. Although therehave been a few reports of low band-gap donor-based BHJ solar cells,none of these solar cells showed much performance improvement overP3HT/PCBM-based solar cells. One problem appears to be that solar cellsbased on these new low band-gap donor materials still exhibit a lowV_(oc) of ˜0.6 V, indicating that the low band-gap donor materials havea HOMO level of ˜5.3 eV and thus, similar stability problems as P3HT.Also important, the BHJ solar cells based on these new donor materialstypically exhibit poor fill factor (<60%).

SUMMARY

In light of the foregoing, the present teachings provide certainoligomeric and polymeric compounds that can be used as organicsemiconductors. Also provided are associated devices and related methodsfor the preparation and use of these compounds. The present compoundscan exhibit properties such as excellent charge transportcharacteristics in ambient conditions, optimized optical absorption,chemical stability, low-temperature processability, large solubility incommon solvents, and processing versatility (e.g., via various solutionprocesses). As a result, optoelectronic devices such as solar cells thatincorporate one or more of the present compounds as a photoactive layercan exhibit high performance in ambient conditions, for example,demonstrating one or more of low band-gap, high fill factor, high opencircuit voltage, and high power conversion efficiency, and preferablyall of these criteria. Similarly, other organic semiconductor-baseddevices such as OLETs can be fabricated efficiently using the organicsemiconductor materials described herein.

The present teachings also provide methods of preparing such compoundsand semiconductor materials, as well as various compositions,composites, and devices that incorporate the compounds and semiconductormaterials disclosed herein.

The foregoing as well as other features and advantages of the presentteachings will be more fully understood from the following figures,description, examples, and claims.

BRIEF DESCRIPTION OF DRAWINGS

It should be understood that the drawings described below are forillustration purpose only. The drawings are not necessarily to scale,with emphasis generally being placed upon illustrating the principles ofthe present teachings. The drawings are not intended to limit the scopeof the present teachings in any way.

FIG. 1 illustrates a representative bulk-heterojunction (BHJ) organicphotovoltaic device (also known as a solar cell) structure, which canincorporate one or more compounds of the present teachings as itsphotoactive layer (as donor and/or acceptor materials).

FIG. 2 shows the transfer plot of a bottom-gate thin film transistordevice having an active layer incorporating a representative co-polymerof the present teachings, where the V_(sd) is −60V.

FIG. 3 shows representative current density-voltage plots of certainphotovoltaic devices having a blend heterojunction layer as follows (a)a thin (˜100 nm) active layer prepared from a mixture of a co-polymer ofthe present teachings and C₆₀PCBM, (b) a thick (˜250 nm) active layerprepared from a mixture of a co-polymer of the present teachings andC₆₀PCBM, (c) a thin (˜100 nm) active layer prepared from a mixture of aco-polymer of the present teachings and C₇₀PCBM, (d) a thick (˜250 nm)active layer prepared from a mixture of a co-polymer of the presentteachings and C₇₀PCBM.

FIG. 4 shows representative EQE-spectra of the four types of devicesdescribed in FIG. 3: (left) devices incorporating C₆₀PCBM as acceptor,(right) devices incorporating C₇₀PCBM as acceptor.

DETAILED DESCRIPTION

The present teachings provide organic semiconductor materials that areprepared from various π-conjugated oligomeric and polymeric compoundshaving typically an electron-rich repeat unit and an electron-poorrepeat unit. Compounds of the present teachings can exhibitsemiconductor behavior such as high carrier mobility and/or good currentmodulation characteristics in a field-effect device, optimized lightabsorption/charge separation in a photovoltaic device, and/or chargetransport/recombination/light emission in a light-emitting device. Inaddition, the present compounds can possess certain processingadvantages such as solution-processability and/or good stability (e.g.,air stability) in ambient conditions. The compounds of the presentteachings can be used to prepare either p-type (donor orhole-transporting), n-type (acceptor or electron-transporting), orambipolar semiconductor materials, which in turn can be used tofabricate various organic or hybrid optoelectronic articles, structuresand devices, including organic photovoltaic devices and organiclight-emitting transistors.

Throughout the application, where compositions are described as having,including, or comprising specific components, or where processes aredescribed as having, including, or comprising specific process steps, itis contemplated that compositions of the present teachings also consistessentially of, or consist of, the recited components, and that theprocesses of the present teachings also consist essentially of, orconsist of, the recited process steps.

In the application, where an element or component is said to be includedin and/or selected from a list of recited elements or components, itshould be understood that the element or component can be any one of therecited elements or components, or the element or component can beselected from a group consisting of two or more of the recited elementsor components. Further, it should be understood that elements and/orfeatures of a composition, an apparatus, or a method described hereincan be combined in a variety of ways without departing from the spiritand scope of the present teachings, whether explicit or implicit herein.

The use of the terms “include,” “includes”, “including,” “have,” “has,”or “having” should be generally understood as open-ended andnon-limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa)unless specifically stated otherwise. In addition, where the use of theterm “about” is before a quantitative value, the present teachings alsoinclude the specific quantitative value itself, unless specificallystated otherwise. As used herein, the term “about” refers to a ±10%variation from the nominal value unless otherwise indicated or inferred.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the present teachings remainoperable. Moreover, two or more steps or actions may be conductedsimultaneously.

As used herein, an “oligomeric compound” (or “oligomer”) or a “polymericcompound” (or “polymer”) refers to a molecule including a plurality ofone or more repeat units connected by covalent chemical bonds. Anoligomeric or polymeric compound can be represented by the generalformula:

*M*

wherein M is the repeat unit or monomer. The degree of polymerizationcan range from 2 to greater than 10,000. For example, for oligomericcompounds, the degree of polymerization can range from 2 to 9; and forpolymeric compounds, the degree of polymerization can range from 10 toabout 10,000. The oligomeric or polymeric compound can have only onetype of repeat unit as well as two or more types of different repeatunits. When a polymeric compound has only one type of repeat unit, itcan be referred to as a homopolymer. When a polymeric compound has twoor more types of different repeat units, the term “copolymer” or“copolymeric compound” can be used instead. The oligomeric or polymericcompound can be linear or branched. Branched polymers can includedendritic polymers, such as dendronized polymers, hyperbranchedpolymers, brush polymers (also called bottle-brushes), and the like.Unless specified otherwise, the assembly of the repeat units in thecopolymer can be head-to-tail, head-to-head, or tail-to-tail. Inaddition, unless specified otherwise, the copolymer can be a randomcopolymer, an alternating copolymer, or a block copolymer. For example,the general formula:

*A_(x)-B_(y)_(n)*

can be used to represent a co-oligomer or copolymer of A and B having xmole fraction of A and y mole fraction of B in the copolymer, where themanner in which comonomers A and B is repeated can be alternating,random, regiorandom, regioregular, or in blocks. The degree ofpolymerization (n) can range from 2 to greater than 10,000.

As used herein, a “cyclic moiety” can include one or more (e.g., 1-6)carbocyclic or heterocyclic rings. The cyclic moiety can be a cycloalkylgroup, a heterocycloalkyl group, an aryl group, or a heteroaryl group(i.e., can include only saturated bonds, or can include one or moreunsaturated bonds regardless of aromaticity), each including, forexample, 3-24 ring atoms and optionally can be substituted as describedherein. In embodiments where the cyclic moiety is a “monocyclic moiety,”the “monocyclic moiety” can include a 3-14 membered aromatic ornon-aromatic, carbocyclic or heterocyclic ring. A monocyclic moiety caninclude, for example, a phenyl group or a 5- or 6-membered heteroarylgroup, each of which optionally can be substituted as described herein.In embodiments where the cyclic moiety is a “polycyclic moiety,” the“polycyclic moiety” can include two or more rings fused to each other(i.e., sharing a common bond) and/or connected to each other via a spiroatom, or one or more bridged atoms. A polycyclic moiety can include an8-24 membered aromatic or non-aromatic, carbocyclic or heterocyclicring, such as a C₈₋₂₄ aryl group or an 8-24 membered heteroaryl group,each of which optionally can be substituted as described herein.

As used herein, “halo” or “halogen” refers to fluoro, chloro, bromo, andiodo.

As used herein, “oxo” refers to a double-bonded oxygen (i.e., ═O).

As used herein, “alkyl” refers to a straight-chain or branched saturatedhydrocarbon group. Examples of alkyl groups include methyl (Me), ethyl(Et), propyl (e.g., n-propyl and iso-propyl), butyl (e.g., n-butyl,iso-butyl, sec-butyl, tert-butyl), pentyl groups (e.g., n-pentyl,iso-pentyl, neo-pentyl), hexyl groups, and the like. In variousembodiments, an alkyl group can have 1 to 40 carbon atoms (i.e., C₁₋₄₀alkyl group), for example, 1-20 carbon atoms (i.e., C₁₋₂₀ alkyl group).In some embodiments, an alkyl group can have 1 to 6 carbon atoms, andcan be referred to as a “lower alkyl group.” Examples of lower alkylgroups include methyl, ethyl, propyl (e.g., n-propyl and iso-propyl),and butyl groups (e.g., n-butyl, iso-butyl, sec-butyl, tert-butyl). Insome embodiments, alkyl groups can be substituted as described herein.An alkyl group is generally not substituted with another alkyl group, analkenyl group, or an alkynyl group.

As used herein, “haloalkyl” refers to an alkyl group having one or morehalogen substituents. At various embodiments, a haloalkyl group can have1 to 40 carbon atoms (i.e., C₁₋₄₀ haloalkyl group), for example, 1 to 20carbon atoms (i.e., C₁₋₂₀ haloalkyl group). Examples of haloalkyl groupsinclude CF₃, C₂F₅, CHF₂, CH₂F, CCl₃, CHCl₂, CH₂Cl, C₂Cl₅, and the like.Perhaloalkyl groups, i.e., alkyl groups where all of the hydrogen atomsare replaced with halogen atoms (e.g., CF₃ and C₂F₅), are includedwithin the definition of “haloalkyl.” For example, a C₁₋₄₀ haloalkylgroup can have the formula C_(s)H_(2s+1−t)X⁰ _(t), where X⁰, at eachoccurrence, is F, Cl, Br or I, s is an integer in the range of 1 to 40,and t is an integer in the range of 1 to 81, provided that t is lessthan or equal to 2s+1. Haloalkyl groups that are not perhaloalkyl groupscan be substituted as described herein.

As used herein, “alkoxy” refers to —O-alkyl group. Examples of alkoxygroups include, but are not limited to, methoxy, ethoxy, propoxy (e.g.,n-propoxy and isopropoxy), t-butoxy, pentoxyl, hexoxyl groups, and thelike. The alkyl group in the —O-alkyl group can be substituted asdescribed herein.

As used herein, “alkylthio” refers to an —S-alkyl group (which, in somecases, can be expressed as —S(O)_(w)-alkyl, wherein w is 0). Examples ofalkylthio groups include, but are not limited to, methylthio, ethylthio,propylthio (e.g., n-propylthio and isopropylthio), t-butylthio,pentylthio, hexylthio groups, and the like. The alkyl group in the—S-alkyl group can be substituted as described herein.

As used herein, “arylalkyl” refers to an alkylaryl group, where thearylalkyl group is covalently linked to the defined chemical structurevia the alkyl group. An arylalkyl group is within the definition of a—Y—C₆₋₁₄ aryl group, where Y is as defined herein. An example of anarylalkyl group is a benzyl group (—CH₂—C₆H₅). An arylalkyl groupoptionally can be substituted, i.e., the aryl group and/or the alkylgroup, can be substituted as disclosed herein.

As used herein, “alkenyl” refers to a straight-chain or branched alkylgroup having one or more carbon-carbon double bonds. Examples of alkenylgroups include ethenyl, propenyl, butenyl, pentenyl, hexenyl,butadienyl, pentadienyl, hexadienyl groups, and the like. The one ormore carbon-carbon double bonds can be internal (such as in 2-butene) orterminal (such as in 1-butene). In various embodiments, an alkenyl groupcan have 2 to 40 carbon atoms (i.e., C₂₋₄₀ alkenyl group), for example,2 to 20 carbon atoms (i.e., C₂₋₂₀ alkenyl group). In some embodiments,alkenyl groups can be substituted as described herein. An alkenyl groupis generally not substituted with another alkenyl group, an alkyl group,or an alkynyl group.

As used herein, “alkynyl” refers to a straight-chain or branched alkylgroup having one or more triple carbon-carbon bonds. Examples of alkynylgroups include ethynyl, propynyl, butynyl, pentynyl, hexynyl, and thelike. The one or more triple carbon-carbon bonds can be internal (suchas in 2-butyne) or terminal (such as in 1-butyne). In variousembodiments, an alkynyl group can have 2 to 40 carbon atoms (i.e., C₂₋₄₀alkynyl group), for example, 2 to 20 carbon atoms (i.e., C₂₋₂₀ alkynylgroup). In some embodiments, alkynyl groups can be substituted asdescribed herein. An alkynyl group is generally not substituted withanother alkynyl group, an alkyl group, or an alkenyl group.

As used herein, “cycloalkyl” refers to a non-aromatic carbocyclic groupincluding cyclized alkyl, alkenyl, and alkynyl groups. In variousembodiments, a cycloalkyl group can have 3 to 24 carbon atoms, forexample, 3 to 20 carbon atoms (e.g., C₃₋₁₄ cycloalkyl group). Acycloalkyl group can be monocyclic (e.g., cyclohexyl) or polycyclic(e.g., containing fused, bridged, and/or spiro ring systems), where thecarbon atoms are located inside or outside of the ring system. Anysuitable ring position of the cycloalkyl group can be covalently linkedto the defined chemical structure. Examples of cycloalkyl groups includecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclopentenyl, cyclohexenyl, cyclohexadienyl, cycloheptatrienyl,norbornyl, norpinyl, norcaryl, adamantyl, and spiro[4.5]decanyl groups,as well as their homologs, isomers, and the like. In some embodiments,cycloalkyl groups can be substituted as described herein.

As used herein, “heteroatom” refers to an atom of any element other thancarbon or hydrogen and includes, for example, nitrogen, oxygen, silicon,sulfur, phosphorus, and selenium.

As used herein, “cycloheteroalkyl” refers to a non-aromatic cycloalkylgroup that contains at least one ring heteroatom selected from O, S, Se,N, P, and Si (e.g., O, S, and N), and optionally contains one or moredouble or triple bonds. A cycloheteroalkyl group can have 3 to 24 ringatoms, for example, 3 to 20 ring atoms (e.g., 3-14 memberedcycloheteroalkyl group). One or more N, P, S, or Se atoms (e.g., N or S)in a cycloheteroalkyl ring may be oxidized (e.g., morpholine N-oxide,thiomorpholine S-oxide, thiomorpholine S,S-dioxide). In someembodiments, nitrogen or phosphorus atoms of cycloheteroalkyl groups canbear a substituent, for example, a hydrogen atom, an alkyl group, orother substituents as described herein. Cycloheteroalkyl groups can alsocontain one or more oxo groups, such as oxopiperidyl, oxooxazolidyl,dioxo-(1H,3H)-pyrimidyl, oxo-2(1H)-pyridyl, and the like. Examples ofcycloheteroalkyl groups include, among others, morpholinyl,thiomorpholinyl, pyranyl, imidazolidinyl, imidazolinyl, oxazolidinyl,pyrazolidinyl, pyrazolinyl, pyrrolidinyl, pyrrolinyl, tetrahydrofuranyl,tetrahydrothiophenyl, piperidinyl, piperazinyl, and the like. In someembodiments, cycloheteroalkyl groups can be substituted as describedherein.

As used herein, “aryl” refers to an aromatic monocyclic hydrocarbon ringsystem or a polycyclic ring system in which two or more aromatichydrocarbon rings are fused (i.e., having a bond in common with)together or at least one aromatic monocyclic hydrocarbon ring is fusedto one or more cycloalkyl and/or cycloheteroalkyl rings. An aryl groupcan have 6 to 24 carbon atoms in its ring system (e.g., C₆₋₂₀ arylgroup), which can include multiple fused rings. In some embodiments, apolycyclic aryl group can have 8 to 24 carbon atoms. Any suitable ringposition of the aryl group can be covalently linked to the definedchemical structure. Examples of aryl groups having only aromaticcarbocyclic ring(s) include phenyl, 1-naphthyl (bicyclic), 2-naphthyl(bicyclic), anthracenyl (tricyclic), phenanthrenyl (tricyclic),pentacenyl (pentacyclic), and like groups. Examples of polycyclic ringsystems in which at least one aromatic carbocyclic ring is fused to oneor more cycloalkyl and/or cycloheteroalkyl rings include, among others,benzo derivatives of cyclopentane (i.e., an indanyl group, which is a5,6-bicyclic cycloalkyl/aromatic ring system), cyclohexane (i.e., atetrahydronaphthyl group, which is a 6,6-bicyclic cycloalkyl/aromaticring system), imidazoline (i.e., a benzimidazolinyl group, which is a5,6-bicyclic cycloheteroalkyl/aromatic ring system), and pyran (i.e., achromenyl group, which is a 6,6-bicyclic cycloheteroalkyl/aromatic ringsystem). Other examples of aryl groups include benzodioxanyl,benzodioxolyl, chromanyl, indolinyl groups, and the like. In someembodiments, aryl groups can be substituted as described herein. In someembodiments, an aryl group can have one or more halogen substituents,and can be referred to as a “haloaryl” group. Perhaloaryl groups, i.e.,aryl groups where all of the hydrogen atoms are replaced with halogenatoms (e.g., —C₆F₅), are included within the definition of “haloaryl.”In certain embodiments, an aryl group is substituted with another arylgroup and can be referred to as a biaryl group. Each of the aryl groupsin the biaryl group can be substituted as disclosed herein.

As used herein, “heteroaryl” refers to an aromatic monocyclic ringsystem containing at least one ring heteroatom selected from oxygen (O),nitrogen (N), sulfur (S), silicon (Si), and selenium (Se) or apolycyclic ring system where at least one of the rings present in thering system is aromatic and contains at least one ring heteroatom.Polycyclic heteroaryl groups include those having two or more heteroarylrings fused together, as well as those having at least one monocyclicheteroaryl ring fused to one or more aromatic carbocyclic rings,non-aromatic carbocyclic rings, and/or non-aromatic cycloheteroalkylrings. A heteroaryl group, as a whole, can have, for example, 5 to 24ring atoms and contain 1-5 ring heteroatoms (i.e., 5-20 memberedheteroaryl group). The heteroaryl group can be attached to the definedchemical structure at any heteroatom or carbon atom that results in astable structure. Generally, heteroaryl rings do not contain O—O, S—S,or S—O bonds. However, one or more N or S atoms in a heteroaryl groupcan be oxidized (e.g., pyridine N-oxide, thiophene S-oxide, thiopheneS,S-dioxide). Examples of heteroaryl groups include, for example, the 5-or 6-membered monocyclic and 5-6 bicyclic ring systems shown below:

where T is O, S, NH, N-alkyl, N-aryl, N-(arylalkyl) (e.g., N-benzyl),SiH₂, SiH(alkyl), Si(alkyl)₂, SiH(arylalkyl), Si(arylalkyl)₂, orSi(alkyl)(arylalkyl). Examples of such heteroaryl rings includepyrrolyl, furyl, thienyl, pyridyl, pyrimidyl, pyridazinyl, pyrazinyl,triazolyl, tetrazolyl, pyrazolyl, imidazolyl, isothiazolyl, thiazolyl,thiadiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, indolyl, isoindolyl,benzofuryl, benzothienyl, quinolyl, 2-methylquinolyl, isoquinolyl,quinoxalyl, quinazolyl, benzotriazolyl, benzimidazolyl, benzothiazolyl,benzisothiazolyl, benzisoxazolyl, benzoxadiazolyl, benzoxazolyl,cinnolinyl, 1H-indazolyl, 2H-indazolyl, indolizinyl, isobenzofuyl,naphthyridinyl, phthalazinyl, pteridinyl, purinyl, oxazolopyridinyl,thiazolopyridinyl, imidazopyridinyl, furopyridinyl, thienopyridinyl,pyridopyrimidinyl, pyridopyrazinyl, pyridopyridazinyl, thienothiazolyl,thienoxazolyl, thienoimidazolyl groups, and the like. Further examplesof heteroaryl groups include 4,5,6,7-tetrahydroindolyl,tetrahydroquinolinyl, benzothienopyridinyl, benzofuropyridinyl groups,and the like. In some embodiments, heteroaryl groups can be substitutedas described herein.

Compounds of the present teachings can include a “divalent group”defined herein as a linking group capable of forming a covalent bondwith two other moieties. For example, compounds of the present teachingscan include a divalent C₁₋₂₀ alkyl group (e.g., a methylene group), adivalent C₂₋₂₀ alkenyl group (e.g., a vinylyl group), a divalent C₂₋₂₀alkynyl group (e.g., an ethynylyl group). a divalent C₆₋₁₄ aryl group(e.g., a phenylyl group); a divalent 3-14 membered cycloheteroalkylgroup (e.g., a pyrrolidylyl), and/or a divalent 5-14 membered heteroarylgroup (e.g., a thienylyl group). Generally, a chemical group (e.g.,—Ar—) is understood to be divalent by the inclusion of the two bondsbefore and after the group.

The electron-donating or electron-withdrawing properties of severalhundred of the most common substituents, reflecting all common classesof substituents have been determined, quantified, and published. Themost common quantification of electron-donating and electron-withdrawingproperties is in terms of Hammett σ values. Hydrogen has a Hammett σvalue of zero, while other substituents have Hammett σ values thatincrease positively or negatively in direct relation to theirelectron-withdrawing or electron-donating characteristics. Substituentswith negative Hammett σ values are considered electron-donating, whilethose with positive Hammett σ values are consideredelectron-withdrawing. See Lange's Handbook of Chemistry, 12th ed.,McGraw Hill, 1979, Table 3-12, pp. 3-134 to 3-138, which lists Hammett σvalues for a large number of commonly encountered substituents and isincorporated by reference herein.

It should be understood that the term “electron-accepting group” can beused synonymously herein with “electron acceptor” and“electron-withdrawing group”. In particular, an “electron-withdrawinggroup” (“EWG”) or an “electron-accepting group” or an“electron-acceptor” refers to a functional group that draws electrons toitself more than a hydrogen atom would if it occupied the same positionin a molecule. Examples of electron-withdrawing groups include, but arenot limited to, halogen or halo (e.g., F, Cl, Br, I), —NO₂, —CN, —NC,—S(R⁰)₂ ⁺, —N(R⁰)₃ ⁺, —SO₃H, —SO₂R⁰, —SO₃R⁰, —SO₂NHR⁰, —SO₂N(R⁰)₂,—COOH, —COR⁰, —COOR⁰, —CONHR⁰, —CON(R⁰)₂, C₁₋₄₀ haloalkyl groups, C₆₋₁₄aryl groups, and 5-14 membered electron-poor heteroaryl groups; where R⁰is a C₁₋₂₀ alkyl group, a C₂₋₂₀ alkenyl group, a C₂₋₂₀ alkynyl group, aC₁₋₂₀ haloalkyl group, a C₁₋₂₀ alkoxy group, a C₆₋₁₄ aryl group, a C₃₋₁₄cycloalkyl group, a 3-14 membered cycloheteroalkyl group, and a 5-14membered heteroaryl group, each of which optionally can be substitutedas described herein. For example, each of the C₁₋₂₀ alkyl group, theC₂₋₂₀ alkenyl group, the C₂₋₂₀ alkynyl group, the C₁₋₂₀ haloalkyl group,the C₁₋₂₀ alkoxy group, the C₆₋₁₄ aryl group, the C₃₋₁₄ cycloalkylgroup, the 3-14 membered cycloheteroalkyl group, and the 5-14 memberedheteroaryl group optionally can be substituted with 1-5 smallelectron-withdrawing groups such as F, Cl, Br, —NO₂, —CN, —NC, —S(R⁰)₂⁺, —N(R⁰)₃ ⁺, —SO₃H, —SO₂R⁰, —SO₃R⁰, —SO₂NHR⁰, —SO₂N(R⁰)₂, —COOH, —COR⁰,—COOR⁰, —CONHR⁰, and —CON(R⁰)₂.

It should be understood that the term “electron-donating group” can beused synonymously herein with “electron donor”. In particular, an“electron-donating group” or an “electron-donor” refers to a functionalgroup that donates electrons to a neighboring atom more than a hydrogenatom would if it occupied the same position in a molecule. Examples ofelectron-donating groups include —OH, —OR⁰, —NH₂, —NHR⁰, —N(R⁰)₂, and5-14 membered electron-rich heteroaryl groups, where R⁰ is a C₁₋₂₀ alkylgroup, a C₂₋₂₀ alkenyl group, a C₂₋₂₀ alkynyl group, a C₆₋₁₄ aryl group,or a C₃₋₁₄ cycloalkyl group.

Various unsubstituted heteroaryl groups can be described aselectron-rich (or π-excessive) or electron-poor (or π-deficient). Suchclassification is based on the average electron density on each ringatom as compared to that of a carbon atom in benzene. Examples ofelectron-rich systems include 5-membered heteroaryl groups having oneheteroatom such as furan, pyrrole, and thiophene; and their benzofusedcounterparts such as benzofuran, benzopyrrole, and benzothiophene.Examples of electron-poor systems include 6-membered heteroaryl groupshaving one or more heteroatoms such as pyridine, pyrazine, pyridazine,and pyrimidine; as well as their benzofused counterparts such asquinoline, isoquinoline, quinoxaline, cinnoline, phthalazine,naphthyridine, quinazoline, phenanthridine, acridine, and purine. Mixedheteroaromatic rings can belong to either class depending on the type,number, and position of the one or more heteroatom(s) in the ring. SeeKatritzky, A. R and Lagowski, J. M., Heterocyclic Chemistry (John Wiley& Sons, New York, 1960).

At various places in the present specification, substituents aredisclosed in groups or in ranges. It is specifically intended that thedescription include each and every individual subcombination of themembers of such groups and ranges. For example, the term “C₁₋₆ alkyl” isspecifically intended to individually disclose C₁, C₂, C₃, C₄, C₅, C₆,C₁-C₆, C₁-C₅, C₁-C₄, C₁-C₃, C₁-C₂, C₂-C₆, C₂-C₅, C₂-C₄, C₂-C₃, C₃-C₆,C₃-C₅, C₃-C₄, C₄-C₆, C₄-C₅, and C₅-C₆ alkyl. By way of other examples,an integer in the range of 0 to is specifically intended to individuallydisclose 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,36, 37, 38, 39, and 40, and an integer in the range of 1 to 20 isspecifically intended to individually disclose 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. Additional examplesinclude that the phrase “optionally substituted with 1-5 substituents”is specifically intended to individually disclose a chemical group thatcan include 0, 1, 2, 3, 4, 5, 0-5, 0-4, 0-3, 0-2, 0-1, 1-5, 1-4, 1-3,1-2, 2-5, 2-4, 2-3, 3-5, 3-4, and 4-5 substituents.

Compounds described herein can contain an asymmetric atom (also referredas a chiral center) and some of the compounds can contain two or moreasymmetric atoms or centers, which can thus give rise to optical isomers(enantiomers) and diastereomers (geometric isomers). The presentteachings include such optical isomers and diastereomers, includingtheir respective resolved enantiomerically or diastereomerically pureisomers (e.g., (+) or (−) stereoisomer) and their racemic mixtures, aswell as other mixtures of the enantiomers and diastereomers. In someembodiments, optical isomers can be obtained in enantiomericallyenriched or pure form by standard procedures known to those skilled inthe art, which include, for example, chiral separation, diastereomericsalt formation, kinetic resolution, and asymmetric synthesis. Thepresent teachings also encompass cis- and trans-isomers of compoundscontaining alkenyl moieties (e.g., alkenes, azo, and imines). It alsoshould be understood that the compounds of the present teachingsencompass all possible regioisomers in pure form and mixtures thereof.In some embodiments, the preparation of the present compounds caninclude separating such isomers using standard separation proceduresknown to those skilled in the art, for example, by using one or more ofcolumn chromatography, thin-layer chromatography, simulated moving-bedchromatography, and high-performance liquid chromatography. However,mixtures of regioisomers can be used similarly to the uses of eachindividual regioisomer of the present teachings as described hereinand/or known by a skilled artisan.

It is specifically contemplated that the depiction of one regioisomerincludes any other regioisomers and any regioisomeric mixtures unlessspecifically stated otherwise.

As used herein, a “leaving group” (“LG”) refers to a charged oruncharged atom (or group of atoms) that can be displaced as a stablespecies as a result of, for example, a substitution or eliminationreaction. Examples of leaving groups include, but are not limited to,halogen (e.g., Cl, Br, I), azide (N₃), thiocyanate (SCN), nitro (NO₂),cyanate (CN), water (H₂O), ammonia (NH₃), and sulfonate groups (e.g.,OSO₂—R, wherein R can be a C₁₋₁₀ alkyl group or a C₆₋₁₄ aryl group eachoptionally substituted with 1-4 groups independently selected from aC₁₋₁₀ alkyl group and an electron-withdrawing group) such as tosylate(toluenesulfonate, OTs), mesylate (methanesulfonate, OMs), brosylate(p-bromobenzenesulfonate, OBs), nosylate (4-nitrobenzenesulfonate, ONs),and triflate (trifluoromethanesulfonate, OTf).

As used herein, a “p-type semiconductor material” or a “donor” materialrefers to a semiconductor material having holes as the majority currentor charge carriers. In some embodiments, when a p-type semiconductormaterial is deposited on a substrate, it can provide a hole mobility inexcess of about 10⁻⁵ cm²/Vs. In the case of field-effect devices, ap-type semiconductor can also exhibit a current on/off ratio of greaterthan about 10.

As used herein, an “n-type semiconductor material” or an “acceptor”material refers to a semiconductor material having electrons as themajority current or charge carriers. In some embodiments, when an n-typesemiconductor material is deposited on a substrate, it can provide anelectron mobility in excess of about 10⁻⁵ cm²/Vs. In the case offield-effect devices, an n-type semiconductor can also exhibit a currenton/off ratio of greater than about 10.

As used herein, “mobility” refers to a measure of the velocity withwhich charge carriers, for example, holes (or units of positive charge)in the case of a p-type semiconductor material and electrons in the caseof an n-type semiconductor material, move through the material under theinfluence of an electric field. This parameter, which depends on thedevice architecture, can be measured using a field-effect device orspace-charge limited current measurements.

As used herein, fill factor (FF) is the ratio (given as a percentage) ofthe actual maximum obtainable power, (P_(m) or V_(mp)*J_(mp)), to thetheoretical (not actually obtainable) power, (J_(sc)×V_(oc)).Accordingly, FF can be determined using the equation:

FF=(V _(mp) *J _(mp))/(J _(sc) *V _(oc))

where J_(mp) and V_(mp) represent the current density and voltage at themaximum power point (P_(m)), respectively, this point being obtained byvarying the resistance in the circuit until J*V is at its greatestvalue; and J_(sc) and V_(oc) represent the short circuit current and theopen circuit voltage, respectively. Fill factor is a key parameter inevaluating the performance of solar cells. Commercial solar cellstypically have a fill factor of about 0.60% or greater.

As used herein, the open-circuit voltage (V_(oc)) is the difference inthe electrical potentials between the anode and the cathode of a devicewhen there is no external load connected.

As used herein, the power conversion efficiency (PCE) of a solar cell isthe percentage of power converted from absorbed light to electricalenergy. The PCE of a solar cell can be calculated by dividing themaximum power point (P_(m)) by the input light irradiance (E, in W/m²)under standard test conditions (STC) and the surface area of the solarcell (A_(c) in m²). STC typically refers to a temperature of 25° C. andan irradiance of 1000 W/m² with an air mass 1.5 (AM 1.5) spectrum.

As used herein, a component (such as a thin film layer) can beconsidered “photoactive” if it contains one or more compounds that canabsorb photons to produce excitons for the generation of a photocurrent.

As used herein, a compound can be considered “ambient stable” or “stableat ambient conditions” when a transistor incorporating the compound asits semiconducting material exhibits a carrier mobility that ismaintained at about its initial measurement when the compound is exposedto ambient conditions, for example, air, ambient temperature, andhumidity, over a period of time. For example, a compound can bedescribed as ambient stable if a transistor incorporating the compoundshows a carrier mobility that does not vary more than 20% or more than10% from its initial value after exposure to ambient conditions,including, air, humidity and temperature, over a 3 day, 5 day, or 10 dayperiod.

As used herein, “solution-processable” refers to compounds (e.g.,polymers), materials, or compositions that can be used in varioussolution-phase processes including spin-coating, printing (e.g., inkjetprinting, screen printing, pad printing, offset printing, gravureprinting, flexographic printing, lithographic printing, mass-printingand the like), spray coating, electrospray coating, drop casting, dipcoating, and blade coating.

Throughout the specification, structures may or may not be presentedwith chemical names. Where any question arises as to nomenclature, thestructure prevails.

The present teachings relate to certain oligomeric and polymericcompounds that can be used as organic semiconductors. The presentcompounds can have good solubility in various common solvents and goodstability in air. When incorporated into optical or optoelectronicdevices including, but not limited to, photovoltaic or solar cells,light emitting diodes, and light emitting transistors, the presentcompounds can confer various desirable performance properties. Forexample, when the present compounds are used in a photoactive layer of asolar cell (e.g., bulk heterojunction devices), the solar cell canexhibit very high power conversion efficiency (e.g., about 4.0% orgreater), fill factor (e.g., about 60% or greater), and/or open circuitvoltage (e.g., about 0.7 V or greater). The present compounds also canbe processed into very efficient solar cells without a thermallyannealing step, thus providing time- and cost-saving benefits andallowing a larger variety of materials to be used in various componentsof the solar cell.

The present teachings provide various conjugated oligomeric andpolymeric compounds, where each compound includes at least two differentmonomeric units. Very generally, the present compounds can berepresented by the formula:

*A_(x)-B_(y)_(n)*

where A and B are different and can be repeated in a random oralternating manner; x and y represent the mole fractions of A and B,respectively, where 0.1≦x≦0.9, 0.1≦y≦0.9, and the sum of x and y isabout 1; and n represents a degree of polymerization in the range from 2to about 10,000 or greater.

More specifically, the present compounds can be represented by theformula:

where A′ and A″ have the definition of A as described above, B′ and B″have the definitions of B as described above, provided that A′ and A″and/or B′ and B″ differ from each other in terms of substitution; x andy represent mole fractions, where 0.1≦x≦0.9, 0.1≦y≦0.9, and the sum of xand y is about 1; and n represents a degree of polymerization in therange from 2 to about 10,000 or greater. For example, one of A′ and A″can be substituted with one or more solubilizing groups while the otheris unsubstituted. Similarly, one or more moieties in B′ can besubstituted while the same moieties in B are unsubstituted. In variousembodiments, the unit comprising x mole fraction of the compound and theunit comprising y mole fraction of the compound, i.e., the units

*A′-B* and *A″-B″*,

can be repeated in a random manner.

For example, the repeat unit A, A′, or A″ can include a conjugatedpolycyclic moiety of the formula:

wherein X is N or CR³ and Y is N or CR⁴, i.e., an optionally substitutedbenzodithienyl moiety of the formula:

or an optionally substituted benzodithiazolyl moiety of the formula:

where R¹, R², R³, and R⁴ independently can be H or a substituent whichcan impart improved desirable properties to the compound as a whole. Forexample, certain substituents including one or more electron-withdrawingor electron-donating moieties can modulate the electronic properties ofthe compound, while substituents that include one or more aliphaticchains can improve the solubility of the compound in organic solvents.

More specifically, each of R¹, R², R³, and R⁴ independently can beselected from H, a halogen, CN, OR′, SR′, C(O)R′, C(O)OR′, SO₂R′, aC₁₋₄₀ alkyl group, a C₂₋₄₀ alkenyl group, a C₂₋₄₀ alkynyl group, a C₁₋₄₀haloalkyl group, a -L′-C₃₋₁₀ cycloalkyl group, a -L′-C₆₋₁₄ aryl group, a-L′-C₆₋₁₄ haloaryl group, a -L′-3-12 membered cycloheteroalkyl group,and a -L′-5-14 membered heteroaryl group;

wherein:

-   -   L′, at each occurrence, independently is selected from a        divalent C₁₋₂₀ alkyl group, a divalent C₁₋₂₀ haloalkyl group,        and a covalent bond;    -   R′ is selected from H, a C₁₋₄₀ alkyl group, a C₂₋₄₀ alkenyl        group, a C₂₋₄₀ alkynyl group, and a C₁₋₄₀ haloalkyl group;    -   each of the C₁₋₄₀ alkyl group, the C₂₋₄₀ alkenyl group, the        C₂₋₄₀ alkynyl group, the C₁₋₄₀ haloalkyl group, the C₁₋₂₀ alkyl        group, the C₁₋₂₀ haloalkyl group, the C₃₋₁₀ cycloalkyl group,        the C₆₋₁₄ aryl group, the C₆₋₁₄ haloaryl group, the 3-12        membered cycloheteroalkyl group, and the 5-14 membered        heteroaryl group, optionally can be substituted with 1-10        substituents independently selected from a halogen, —CN, NO₂,        OH, —NH₂, —NH(C₁₋₂₀ alkyl), —N(C₁₋₂₀ alkyl)₂, —S(O)₂OH, —CHO,        —C(O)—C₁₋₂₀ alkyl, —C(O)OH, —C(O)—OC₁₋₂₀ alkyl, —C(O)NH₂,        —C(O)NH—C₁₋₂₀ alkyl, —C(O)N(C₁₋₂₀ alkyl)₂, —OC₁₋₂₀ alkyl, —SiH₃,        —SiH(C₁₋₂₀ alkyl)₂, —SiH₂ (C₁₋₂₀ alkyl), and —Si(C₁₋₂₀ alkyl)₃;        and    -   one or more non-adjacent-CH— groups in the C₁₋₄₀ alkyl group,        the C₂₋₄₀ alkenyl group, the C₂₋₄₀ alkynyl group, the C₁₋₄₀        haloalkyl group, the C₁₋₂₀ alkyl group, or the C₁₋₂₀ haloalkyl        group, can be replaced by a group independently selected from        —O—, —S—, —NH—, —N(C₁₋₂₀ alkyl)-, —Si(C₁₋₂₀ alkyl)₂—, —C(O)—,        —C(O)O—, —OC(O)—, and —OC(O)O—.

In certain embodiments, at least one of R¹, R², R³, and R⁴ independentlycan be a small functional group such as a halogen, CN, OR, C(O)R′,C(O)OR′, or SO₂R′, where R′ can be H or a lower alkyl group.

In certain embodiments, at least one of R¹, R², R³, and R⁴ independentlycan be a linear or branched C₃₋₄₀ alkyl group, examples of which includean n-hexyl group, an n-octyl group, an n-dodecyl group, a 1-methylpropylgroup, a 1-methylbutyl group, a 1-methylpentyl group, a 1-methylhexylgroup, a 1-ethylpropyl group, a 1-ethylbutyl group, a 1,3-dimethylbutylgroup, a 2-ethylhexyl group, a 2-hexyloctyl group, a 2-octyldodecylgroup, and a 2-decyltetradecyl group. In certain embodiments, at leastone of R¹, R², R³, and R⁴ independently can be a linear or branchedC₃₋₄₀ alkenyl group (such as the linear or branched C₃₋₄₀ alkyl groupsspecified above but with one or more saturated bonds replaced byunsaturated bonds). In particular embodiments, at least one of R¹, R²,R³, and R⁴ independently can be a branched C₃₋₂₀ alkyl group or abranched C₃₋₂₀ alkenyl group.

In certain embodiments, at least one of R¹, R², R³, and R⁴ independentlycan be a linear or branched C₆₋₄₀ alkyl or alkenyl group, an arylalkylgroup (e.g., a benzyl group) substituted with a linear or branched C₆₋₄₀alkyl or alkenyl group, an aryl group (e.g., a phenyl group) substitutedwith a linear or branched C₆₋₄₀ alkyl or alkenyl group, or a biarylgroup (e.g., a biphenyl group) substituted with a linear or branchedC₆₋₄₀ alkyl or alkenyl group, wherein each of these groups optionallycan be substituted with 1-5 halo groups (e.g., F). In some embodiments,at least one of R¹, R², R³, and R⁴ independently can be a biaryl groupwherein the two aryl groups are covalently linked via a linker. Forexample, the linker can be a divalent C₁₋₄₀ alkyl group wherein one ormore non-adjacent CH₂ groups optionally can be replaced by —O—, —S—, or—Se—, i.e., O, S, and/or Se atoms are not linked directly to oneanother. The linker can include other heteroatoms and/or functionalgroups as described herein.

To further illustrate, in certain embodiments, R¹, R², R³, and R⁴independently can be selected from H or -L′-R^(a), where R^(a) isselected from a C₁₋₄₀ alkyl group, a C₂₋₄₀ alkenyl group, a C₂₋₄₀alkynyl group, and a C₁₋₄₀ haloalkyl group, each of which optionally canbe substituted with 1-10 substituents independently selected from ahalogen, —CN, NO₂, OH, —NH₂, —NH(C₁₋₂₀ alkyl), —N(C₁₋₂₀ alkyl)₂,—S(O)₂OH, —CHO, —C(O)—C₁₋₂₀ alkyl, —C(O)OH, —C(O)—OC₁₋₂₀ alkyl,—C(O)NH₂, —C(O)NH—C₁₋₂₀ alkyl, —C(O)N(C₁₋₂₀ alkyl)₂, —OC₁₋₂₀ alkyl,—SiH₃, —SiH(C₁₋₂₀ alkyl)₂, —SiH₂ (C₁₋₂₀ alkyl), and —Si(C₁₋₂₀ alkyl)₃;and L′ is a covalent bond or a linker comprising one or moreheteroatoms. For example, L′ can be a linker selected from —Y—O—Y—,—Y—[S(O)_(w)]-Y—, —Y—C(O)—Y—, —Y—[NR^(c)C(O)]-Y—, —Y—[C(O)NR^(c)]—,—Y—NR^(c)—Y—, —Y—[SiR^(c)2]-Y—, where Y, at each occurrence,independently is selected from a divalent C₁₋₂₀ alkyl group, a divalentC₂₋₂₀ alkenyl group, a divalent C₂₋₂₀ haloalkyl group, and a covalentbond; R^(c) is selected from H, a C₁₋₆alkyl group, a C₆₋₁₄ aryl group,and a —C₁₋₆alkyl-C₆₋₁₄ aryl group; and w is 0, 1, or 2. In someembodiments, R¹, R², R³, and R⁴ independently can be selected from H, aC₃₋₄₀ alkyl group, an —O—C₃₋₄₀ alkyl group, an —S—C₃₋₄₀ alkyl group, aC₄-40 alkenyl group, a C₄-40 alkynyl group, and a C₃₋₄₀ haloalkyl group,where each of these groups can be linear or branched, and optionally canbe substituted as described herein.

In other embodiments, one or more of R¹, R², R³, and R⁴ independentlycan include one or more cyclic moieties.

In various embodiments, the conjugated polycyclic moiety:

can be symmetrically substituted, that is, R¹ and R² can be identicalgroups, and/or when X and Y are CR³ and CR⁴, respectively, R³ and R⁴ canbe identical groups. For example, each of R¹ and R² and/or each of R³and R⁴ can be a branched C₃₋₄₀ alkyl group, a branched C₃₋₄₀ haloalkylgroup, a branched C₃₋₄₀ alkoxy group, or a branched C₃₋₄₀ alkylthiogroup.

The repeat unit B, B′, or B″ in the present oligomeric or polymericcompounds can have the formula:

—(Ar)-M-(Ar)—

where each Ar can be an optionally substituted 5-10 membered aryl orheteroaryl group; and M can be an optionally substituted benzofusedheteroaryl moiety as described herein.

Accordingly, in some embodiments, compounds according to the presentteachings can be represented by formula I:

wherein:

each M is an optionally substituted benzofused heteroaryl moietycomprising 1-6 heteroatoms;

X is N or CR³;

Y is N or CR⁴;

each of R¹, R², R³ and R⁴ independently is selected from H and -L-R,

wherein:

-   -   L, at each occurrence, independently is selected from O, S, and        a covalent bond; and    -   R, at each occurrence, independently is a C₁₋₄₀ alkyl group;

R⁷, at each occurrence, independently is selected from a C₁₋₄₀ alkylgroup, a C₁₋₄₀ haloalkyl group, a C₁₋₄₀ alkoxy group, and a C₁₋₄₀alkylthio group; and

x and y are real numbers representing mole fractions, wherein 0.1≦x≦0.9,0.1≦y≦0.9, and the sum of x and y is about 1.

For example, the optionally substituted benzofused heteroaryl moiety canbe represented by the formula:

wherein Het, at each occurrence, is a monocyclic moiety including atleast one heteroatom in its ring, and R⁵ and R⁶ independently can be Hor -L-R, where L and R are as defined herein.

To illustrate, M can be selected from:

wherein R⁸ is H or a C₁₋₄₀ alkyl group, and R⁵ and R⁶ are as definedherein.

In particular embodiments, M can be selected from:

wherein R⁵ and R⁶ are as defined herein. For example, R⁵ and R⁶ can be Hor a C₁₋₄₀ alkyl group.

Accordingly, in certain embodiments, copolymers according to the presentteachings can be represented by Formula II:

wherein R¹, R², R⁵, R⁶, R⁷, Z, x and y are as defined herein. Forexample, R⁵ and R⁶ independently can be H or a C₁₋₄₀ alkyl group; andeach R⁷ can be a C₁₋₄₀ alkyl group or a C₁₋₄₀ alkoxy group.

In particular embodiments, certain copolymers according to the presentteachings can be represented by Formula III:

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, x and y are as defined herein. Forexample, R⁵ and R⁶ independently can be H or a C₁₋₄₀ alkyl group; andeach R⁷ can be a C₁₋₄₀ alkyl group or a C₁₋₄₀ alkoxy group. To furtherillustrate, compounds of formula III can be represented by a formulaselected from:

wherein R¹, R², R³, R⁴, R⁷, x and y are as defined herein. In someembodiments, R³ and R⁴ can be H, and R¹ and R² can be -L-R, wherein Land R are as defined herein. In other embodiments, R¹ and R² can be H,and R³ and R⁴ can be -L-R, wherein L and R are as defined herein. Forexample, -L-R can be selected from a C₃₋₄₀ alkyl group (R), a C₃₋₄₀alkoxy group (—O—R), and a C₃₋₄₀ alkylthio group (—S—R).

In certain embodiments, copolymers of the present teachings can berepresented by formula IV:

including a formula selected from:

wherein R is a C₁₋₄₀ alkyl group, and R⁷, x and y are as defined herein.For example, in some embodiments, R can be a branched C₆₋₂₀ alkyl group,R⁷ can be a linear C₆₋₂₀ alkyl group. In other embodiments, R can be abranched C₆₋₂₀ alkyl group, R⁷ can be a linear C₆₋₂₀ alkoxy group. Themole fractions x and y, respectively, can range between about 0.2 andabout 0.8, i.e., 0.2≦x≦0.8 and 0.2≦y≦0.8, provided that the sum of x andy is about 1.

To further illustrate, certain copolymers of formula IV can berepresented by a formula selected from:

wherein R, at each occurrence, independently can be a C₆₋₂₀ alkyl group,and x and y are as defined herein.

In certain embodiments, copolymers of the present teachings can berepresented by formula V:

including a formula selected from:

wherein R is a C₁₋₄₀ alkyl group, and R⁷, x and y are as defined herein.For example, in some embodiments, R can be a branched C₆₋₂₀ alkyl group,R⁷ can be a linear C₆₋₂₀ alkyl group. In other embodiments, R can be abranched C₆₋₂₀ alkyl group, R⁷ can be a linear C₆₋₂₀ alkoxy group. Themole fractions x and y, respectively, can range between about 0.2 andabout 0.8, i.e., 0.2≦x≦0.8 and 0.2≦y≦0.8, provided that the sum of x andy is about 1.

To further illustrate, certain copolymers of formula V can berepresented by a formula selected from:

wherein R, at each occurrence, independently can be a C₆₋₂₀ alkyl group,and x and y are as defined herein.

In certain embodiments, the optionally substituted benzodithienyl orbenzodithiazolyl groups in formula I can be replaced by anotheroptionally substituted conjugated polycyclic moiety [π-2], where [π-2]is incorporated into the backbone of the compound via atoms belonging totwo different rings. That is, the A′ and A″ groups can be an optionallysubstituted benzodithienyl or benzodithiazolyl group or some otheroptionally substituted conjugated polycyclic moiety [π-2].

For example, [π-2] can be an optionally substituted polycyclic moietyselected from:

where R⁸, at each occurrence, independently can be H or a C₁₋₄₀ alkylgroup.

In the various copolymers described herein (including compounds offormulae I, II, III, IV, and V), the unit comprising x mole fraction ofthe copolymer and the unit comprising y mole fraction of the copolymercan be repeated in a random manner. In addition, in these compounds, theunit comprising x mole fraction of the copolymer (i.e., the unitincluding the unsubstituted thienyl groups) can be present at a highermole fraction than the unit comprising y mole fraction of the copolymer(i.e., the unit including the substituted thienyl groups). Morespecifically, x can be at least about 0.5, that is, 0.5≦x≦0.9 and0.1≦y≦0.5, where the sum of x and y is about 1. In particularembodiments, x and y can be real numbers in the range of 0.5≦x≦0.8 and0.2≦y≦0.5, where the sum of x and y is about 1. Further, the degree ofpolymerization (n) can be in the range from 5 to about 10,000. Forexample, the degree of polymerization (n) can be in the range from 10 toabout 10,000.

The inventors surprisingly have found that the compounds of formulae I,II, III, IV, and V can provide exceptional performance improvements inorganic photovoltaic devices. The performance improvements can includehigh power conversion efficiency (e.g., about 4.0% or greater, about4.5% or greater, about 5.0% or greater, or about 5.5% or greater), lowband-gap (e.g., about 1.60 eV or lower, about 1.55 eV or lower, or about1.50 eV or lower), high fill factor (e.g., about 60% or greater, about65% or greater, or about 70% or greater), and/or high open circuitvoltage (e.g., about 0.6 V or greater, about 0.7 V or greater, or about0.8 V or greater). More surprisingly, the inventors have observed thatwhen a compound of formula I, II, III, IV, or V is used in thephotoactive material of a photovoltaic device, the performance of thedevice often is markedly better than a comparative device incorporatinga copolymer of either the unit comprising x mole fraction of thecopolymer (i.e., the unit including the unsubstituted thienyl groups)alone or a copolymer of the unit comprising y mole fraction of thecopolymer (i.e., the unit including the substituted thienyl groups)alone, but not a copolymer of both units as in the present copolymers.The performance improvements can include higher power conversionefficiency, lower band-gap, higher fill factor, and/or higher opencircuit voltage compared to the comparative device. In certainembodiments, improvements in band-gap, fill factor and open circuitvoltage are observed simultaneously in the same device using a copolymeraccording to the present teachings. In certain embodiments, improvementsin at least three of the four criteria are observed. In particularembodiments, improvements in all four criteria are observed.

Compounds of the present teachings and monomers leading to the presentcompounds can be prepared according to procedures analogous to thosedescribed in the Examples. In particular, Stille coupling or Suzukicoupling reactions can be used to prepare co-polymeric compoundsaccording to the present teachings with high molecular weights and inhigh yields (≧75%) and purity, as confirmed by ¹H NMR spectra, elementalanalysis, and/or GPC measurements.

Alternatively, the present compounds can be prepared from commerciallyavailable starting materials, compounds known in the literature, or viaother readily prepared intermediates, by employing standard syntheticmethods and procedures known to those skilled in the art. Standardsynthetic methods and procedures for the preparation of organicmolecules and functional group transformations and manipulations can bereadily obtained from the relevant scientific literature or fromstandard textbooks in the field. It will be appreciated that wheretypical or preferred process conditions (i.e., reaction temperatures,times, mole ratios of reactants, solvents, pressures, etc.) are given,other process conditions can also be used unless otherwise stated.Optimum reaction conditions can vary with the particular reactants orsolvent used, but such conditions can be determined by one skilled inthe art by routine optimization procedures. Those skilled in the art oforganic synthesis will recognize that the nature and order of thesynthetic steps presented can be varied for the purpose of optimizingthe formation of the compounds described herein.

The processes described herein can be monitored according to anysuitable method known in the art. For example, product formation can bemonitored by spectroscopic means, such as nuclear magnetic resonancespectroscopy (NMR, e.g., ¹H or ¹³C), infrared spectroscopy (IR), opticalabsorption/emission spectroscopy (e.g., UV-visible), mass spectrometry(MS), or by chromatography such as high pressure liquid chromatography(HPLC), gas chromatography (GC), gel-permeation chromatography (GPC), orthin layer chromatography (TLC).

The reactions or the processes described herein can be carried out insuitable solvents which can be readily selected by one skilled in theart of organic synthesis. Suitable solvents typically are substantiallynonreactive with the reactants, intermediates, and/or products at thetemperatures at which the reactions are carried out, i.e., temperaturesthat can range from the solvent's freezing temperature to the solvent'sboiling temperature. A given reaction can be carried out in one solventor a mixture of more than one solvent. Depending on the particularreaction step, suitable solvents for a particular reaction step can beselected.

Certain embodiments disclosed herein can be stable in ambient conditions(“ambient stable”) and soluble in common solvents. As used herein, acompound can be considered electrically “ambient stable” or “stable atambient conditions” when a transistor incorporating the compound as itssemiconducting material exhibits a carrier mobility that is maintainedat about its initial measurement when the compound is exposed to ambientconditions, for example, air, ambient temperature, and humidity, over aperiod of time. For example, a compound according to the presentteachings can be described as ambient stable if a transistorincorporating the compound shows a carrier mobility that does not varymore than 20% or more than 10% from its initial value after exposure toambient conditions, including, air, humidity and temperature, over a 3day, 5 day, or 10 day period. In addition, a compound can be consideredambient stable if the optical absorption of the corresponding film doesnot vary more than 20% (preferably, does not vary more than 10%) fromits initial value after exposure to ambient conditions, including air,humidity and temperature, over a 3 day, 5 day, or 10 day period.

As used herein, a compound can be considered soluble in a solvent whenat least 0.1 mg of the compound can be dissolved in 1 mL of the solvent.Examples of common organic solvents include petroleum ethers;acetonitrile; aromatic hydrocarbons such as benzene, toluene, xylene,and mesitylene; ketones such as acetone, and methyl ethyl ketone; etherssuch as tetrahydrofuran, dioxane, bis(2-methoxyethyl)ether, diethylether, di-isopropyl ether, and t-butyl methyl ether; alcohols such asmethanol, ethanol, butanol, and isopropyl alcohol; aliphatichydrocarbons such as hexanes; esters such as methyl acetate, ethylacetate, methyl formate, ethyl formate, isopropyl acetate, and butylacetate; amides such as dimethylformamide and dimethylacetamide;sulfoxides such as dimethylsulfoxide; halogenated aliphatic and aromatichydrocarbons such as dichloromethane, chloroform, ethylene chloride,chlorobenzene, dichlorobenzene, and trichlorobenzene; and cyclicsolvents such as cyclopentanone, cyclohexanone, and 2-methypyrrolidone.

The present compounds can be fabricated into various articles ofmanufacture using solution processing techniques in addition to othermore expensive processes such as vapor deposition. Various solutionprocessing techniques have been used with organic electronics. Commonsolution processing techniques include, for example, spin coating,drop-casting, zone casting, dip coating, blade coating, or spraying.Another example of solution processing technique is printing. As usedherein, “printing” includes a noncontact process such as inkjetprinting, microdispensing and the like, and a contact process such asscreen-printing, gravure printing, offset printing, flexographicprinting, lithographic printing, pad printing, microcontact printing andthe like.

Compounds of the present teachings can be used alone or in combinationwith other compounds to prepare semiconductor materials (e.g.,compositions and composites), which in turn can be used to fabricatevarious articles of manufacture, structures, and devices. In someembodiments, semiconductor materials incorporating one or more compoundsof the present teachings can exhibit p-type semiconductor activity,ambipolar activity, light absorption, and/or light emission.

The present teachings, therefore, further provide methods of preparing asemiconductor material. The methods can include preparing a composition(e.g., a solution or dispersion) that includes one or more compoundsdisclosed herein dissolved or dispersed in a liquid medium such as asolvent or a mixture of solvents, depositing the composition on asubstrate to provide a semiconductor material precursor, and processing(e.g., heating) the semiconductor precursor to provide a semiconductormaterial (e.g., a photoactive layer) that includes a compound disclosedherein. In various embodiments, the liquid medium can be an organicsolvent, an inorganic solvent such as water, or combinations thereof. Insome embodiments, the composition can further include one or moreadditives independently selected from viscosity modulators, detergents,dispersants, binding agents, compatibilizing agents, curing agents,initiators, humectants, antifoaming agents, wetting agents, pHmodifiers, biocides, and bacteriostats. For example, surfactants and/orpolymers (e.g., polystyrene, polyethylene, poly-alpha-methylstyrene,polyisobutene, polypropylene, polymethylmethacrylate, and the like) canbe included as a dispersant, a binding agent, a compatibilizing agent,and/or an antifoaming agent. In some embodiments, the depositing stepcan be carried out by printing, including inkjet printing and variouscontact printing techniques (e.g., screen-printing, gravure printing,offset printing, pad printing, lithographic printing, flexographicprinting, and microcontact printing). In other embodiments, thedepositing step can be carried out by spin coating, drop-casting, zonecasting, dip coating, blade coating, or spraying.

Various articles of manufacture including optical devices,optoelectronic devices, and electronic devices such as thin filmsemiconductors, photovoltaic devices, photodetectors, organic lightemitting devices such as organic light emitting transistors (OLETs),that make use of the compounds disclosed herein are within the scope ofthe present teachings as are methods of making the same. The presentcompounds can offer processing and operation advantages in thefabrication and/or the use of these devices.

For example, articles of manufacture such as the various devicesdescribed herein can be an optical or optoelectronic device including afirst electrode, a second electrode, and a photoactive componentdisposed between the first electrode and the second electrode, where thephotoactive component includes a compound of the present teachings.

In various embodiments, the optical or optoelectronic device can beconfigured as a solar cell, in particular, a bulk heterojunction solarcell. Compounds of the present teachings can exhibit broad opticalabsorption and/or a tuned redox properties and bulk carrier mobilities,making them desirable for such applications. In various embodiments, thebulk heterojunction solar cells according to the present teachings canincorporate a blend material (e.g., a blended film) including a compoundof the present teachings as the donor material and an acceptor materialas the photoactive layer. While in most state-of-the-art devices, thethickness of the blended film often is limited to about 100 nm or less(to obtain good device performance), the inventors have observedcomparable performance with films prepared from the copolymers describedherein in a broad thickness range, specifically, with thin films havinga thickness of about 100 nm or less, as well as films having a thicknessgreater than about 200 nm.

Typical acceptor materials include fullerene-based compounds. Fullerenesuseful in the present teachings can have a broad range of sizes (numberof carbon atoms per molecule). The term fullerene as used hereinincludes various cage-like molecules of pure carbon, includingBuckministerfullerene (C₆₀) “bucky ball” and the related “spherical”fullerenes as well as carbon nanotubes. Fullerenes can be selected fromthose known in the art ranging from, for example, C20-C1000. In certainembodiments, the fullerene can be selected from the range of C60 to C96.In particular embodiments, the fullerene can be C60 or C70, such as[60]PCBM, or [70]PCBM. In some embodiments, chemically modifiedfullerenes can be used, provided that the modified fullerene retainsacceptor-type and electron mobility characteristics. Other acceptormaterials can be used in place of fullerenes, provided that they havethe required acceptor-type and electron mobility characteristics. Forexample, the acceptor material can be various organic small molecules,polymers, carbon nanotubes, or inorganic particles (quantum dots,quantum rods, quantum tripods, TiO₂, ZnO etc.).

A photoactive component according to the present teachings can beprepared as a blended film deposited from a solution or dispersioncontaining a mixture of one or more of the present compounds and anacceptor compound such as fullerene (e.g., PCBM). The ratio of thepresent polymer to the acceptor compound can range from about 10:1 toabout 1:10 by weight; for example, from about 5:1 to about 1:5 byweight, from about 3:1 to about 1:3 by weight, or from about 2:1 toabout 1:2 by weight. The photoactive layer also can contain a polymericbinder, which can be present from about 5 to about 95% by weight. Thepolymeric binder, for example, can be a semicrystalline polymer selectedfrom polystyrene (PS), high density polyethylene (HDPE), polypropylene(PP) and polymethylmethacrylate (PMMA).

FIG. 1 illustrates a representative structure of a bulk-heterojunctionorganic solar cell which can incorporate one or more compounds of thepresent teachings as the donor and/or acceptor materials. As shown, arepresentative solar cell generally includes a substrate 20, an anode22, a cathode 26, and a photoactive layer 24 between the anode and thecathode that can incorporate one or more compounds of the presentteachings as the electron donor (p-channel) and/or electron acceptor(n-channel) materials. In some embodiments, an optional smoothing layercan be present between the anode and the photoactive layer.

The substrate can be, for example, glass or a flexible substrate (e.g.,plastic). The electrodes can be composed of metals or transparentconducting oxides such as indium tin oxide (ITO), gallium indium tinoxide (GITO), and zinc indium tin oxide (ZITO). For example, the cathodecan be composed of aluminum or calcium, while the anode can be composedof ITO.

In various embodiments, an optional smoothing layer can be presentbetween the anode and the photoactive layer. For example, the smoothinglayer can include a film of 3,4-polyethylenedioxythiophene (PEDOT), or3,4-polyethylenedioxythiophene: polystyrene-sulfonate (PEDOT:PSS).

In certain embodiments, a solar cell according to the present teachingscan include a transparent glass substrate onto which an electrode layer(anode) made of indium tin oxide (ITO) is applied. This electrode layercan have a relatively rough surface, and a smoothing layer made of apolymer, typically PEDOT:PSS made electrically conductive throughdoping, can be applied on top of the electrode layer to enhance itssurface morphology. The photoactive layer generally is made of twocomponents as described above, and can have a layer thickness of, e.g.,about 100 nm to a few m. Before a counter electrode is applied(cathode), an electrically insulating transition layer can be appliedonto the photoactive layer. This transition layer can be made of analkali halogenide, e.g., LiF, and can be vapor-deposited in vacuum.

Another aspect of the present teachings relates to methods offabricating an organic light-emitting transistor or an organiclight-emitting diode (OLED) that incorporates one or more semiconductormaterials of the present teachings. For example, in an OLED, one or morecompounds of the present teachings can be used as electron-transportingand/or emissive and/or hole-transporting materials. An OLED generallyincludes a substrate, a transparent anode (e.g., ITO), a cathode (e.g.,metal), and one or more organic layers which can incorporate one or morecompounds of the present teachings as hole-transporting (p-channel)and/or emissive and/or electron-transporting (n-channel) materials. Inembodiments where the present compounds only have one or two of theproperties of hole transport, electron transport, and emission, thepresent compounds can be blended with one or more further organiccompounds having the remaining required property or properties.

In other embodiments, the article of manufacture can be an electronic oroptoelectronic device (e.g., an organic light-emitting transistor)including a first electrode, a second electrode, and a semiconductingcomponent in contact with the first electrode and the second electrode,where the semiconducting component includes a compound of the presentteachings. These devices can include a composite having a semiconductingcomponent (or semiconductor material) of the present teachings and asubstrate component and/or a dielectric component. The substratecomponent can be selected from doped silicon, an indium tin oxide (ITO),ITO-coated glass, ITO-coated polyimide or other plastics, aluminum orother metals alone or coated on a polymer or other substrate, a dopedpolythiophene, and the like. The dielectric component can be preparedfrom inorganic dielectric materials such as various oxides (e.g., SiO₂,Al₂O₃, HfO₂), organic dielectric materials such as various polymericmaterials (e.g., polycarbonate, polyester, polystyrene,polyhaloethylene, polyacrylate), and self-assembledsuperlattice/self-assembled nanodielectric (SAS/SAND) materials (e.g.,as described in Yoon, M-H. et al., PNAS, 102 (13): 4678-4682 (2005), theentire disclosure of which is incorporated by reference herein), as wellas hybrid organic/inorganic dielectric materials (e.g., described inU.S. patent application Ser. No. 11/642,504, the entire disclosure ofwhich is incorporated by reference herein). In some embodiments, thedielectric component can include the crosslinked polymer blendsdescribed in U.S. patent application Ser. Nos. 11/315,076, 60/816,952,and 60/861,308, the entire disclosure of each of which is incorporatedby reference herein. The composite also can include one or moreelectrical contacts. Suitable materials for the source, drain, and gateelectrodes include metals (e.g., Au, Al, Ni, Cu), transparent conductingoxides (e.g., ITO, IZO, ZITO, GZO, GIO, GITO), and conducting polymers(e.g., poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)(PEDOT:PSS), polyaniline (PANI), polypyrrole (PPy)). One or more of thecomposites described herein can be embodied within various organicelectronic, optical, and optoelectronic devices such as organicphotovoltaics (OPV) and organic light-emitting transistors (OLETs) asdescribed above.

The following examples are provided to illustrate further and tofacilitate the understanding of the present teachings and are not in anyway intended to limit the invention.

All reagents were purchased from commercial sources and used withoutfurther purification unless otherwise noted. Specifically, dioxane,dichlorobenzene (DCB), chloroform (CHCl₃), and other chlorinatedhydrocarbons (CHCs) used for dielectric and semiconductor formulationswere purchased from Sigma Aldrich and distilled before use. Anhydroustetrahydrofuran (THF) was distilled from Na/benzophenone. ConventionalSchlenk techniques were used and reactions were carried out under N₂unless otherwise noted.

Characterization data are provided in some cases by ¹H-NMR, ¹³C-NMR,and/or elemental analysis. NMR spectra were recorded on an Inova 500 NMRspectrometer (¹H, 500 MHz). Elemental analyses were performed by MidwestMicrolab, LLC. Polymer molecular weights were determined on a Waters GPCsystem (Waters Pump 510) in THF at room temperature versus polystyrenestandards.

Example 1 Synthesis of Monomers Example 1a Preparation of4,8-didodecyl-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

Step 1: Preparation of 4,8-didodecynylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of dodecyne (17.5 mL, 81.7 mmol) in THF (20 mL) in a 250mL flask equipped with a condenser under an argon atmosphere was addeddropwise 36 mL (72 mmol) of a 2 M solution of isopropylmagnesiumchloride in THF at room temperature. After addition, the reactionmixture was heated at 50° C. for 95 min and cooled to room temperature.4,8-Dihydrobenzo[1,2-b:4,5-b′]dithiophene-4,8-dione (3 g, 13.6 mmol) wasadded, and the mixture was heated at 50° C. for 1 hour before coolingdown to room temperature. Subsequently, a solution of 20 g of SnCl₂ in50 mL 10% aqueous HCl solution was added in a dropwise fashion followedby further heating at 60° C. for 1 hour. After the reaction, brine (30mL) was added. The organic phase was separated and evaporated undervacuum. The residue was diluted with MeOH (100 mL) and filtered. Thesolid was washed with MeOH several times. The brown solid was purifiedby column chromatography with CHCl₃:hexane 5:6 as eluent.Recrystallization of the crude product collected from flashchromatography from hexane gave 4.03 g (57% yield) of a pale yellowcrystal after drying in vacuo. ¹H NMR (CDCl₃, 500 MHz), δ=7.59 (d, J=5.5Hz, 2H), 7.51 (d, J=6.0 Hz, 2H), 2.65 (t, J=6.5 Hz, 4H), 1.70-1.80 (m,4H), 1.56-1.65 (m, 4H), 1.22-1.47 (m, 24H), 0.90 (t, J=6.5 Hz, 6H).

Step 2: Preparation of 4,8-didodecylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of 4,8-didodecynbenzo[1,2-b:4,5-b′]dithiophene (1.04 g, 2mmol) in THF (33 mL) in a round-bottomed flask was added 10% Pd/C (0.21g, 0.2 mmol). The mixture was stirred under a hydrogen atmosphere atroom temperature for 24 h. After filtration the solvent was removed byvacuum evaporation, and the residue was passed through a silica gelflash column with hexane as eluent to give a white solid (530 mg, yield50%).

¹H NMR (CDCl₃, 500 MHz) δ=7.48 (d, J=5.5 Hz, 2H), 7.47 (d, J=5.5 Hz,2H), 3.19 (t, J=7.5 Hz, 4H), 1.76-1.89 (m, 4H), 1.42-1.53 (m, 4H),1.19-1.42 (bs, 32H), 0.90 (t, J=7.0 Hz, 6H).

Step 3: Preparation of4,8-didodecyl-2,6-Bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of 4,8-didodecylbenzo[1,2-b:4,5-b′]dithiophene (553 mg,1.05 mmol) in dry tetrahydrofuran (16 mL) was added n-butyllithium (2.5M in hexane, 0.92 mL, 2.31 mmol) at −78° C. After 1 hour, trimethyltinchloride (488 mg, 2.45 mmol) was added in one portion. The mixture wasstirred at room temperature for 2 hours, poured into water and extractedwith ether three times. The organic layer was washed with brine anddried over anhydrous MgSO₄. Upon evaporating the solvent, a pale yellowoil was obtained which is recrystallized from EtOH to give a white solid(524 mg, yield 58%). ¹H NMR (CDCl₃, 500 MHz) δ=7.51 (s, 2H), 3.22 (t,J=8.0 Hz, 4H), 1.76-1.91 (m, 4H), 1.36-1.42 (m, 4H), 1.22-1.42 (bs,32H), 0.91 (t, J=7.0 Hz, 6H), 0.47 (s, 18H). See also, Chem. Mater.2006, 18, 3237.

Example 1b Preparation of4,8-dioctyl-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

Step 1: Preparation of 4,8-dioctylbenzo[1,2-b:4,5-b′]dithiophene

To a 100 mL flask under nitrogen was added4,8-dihydrobenzo[1,2-b:4,5-b′]dithiophene-4,8-dione (1.1 g, 5.0 mmol)and anhydrous THF (10 mL). The mixture was heated to reflux andoctylmagnesium bromide (20 mmol, 10 mL, 2.0 M in Et₂O) was addeddropwise. After refluxing for 2 hours more, SnCl₂ solution (7.3 g in 19mL 10% HCl) was slowly added dropwise. The mixture was kept at 60° C.for 1 hour. After cooling down, the organic phase was separated. Thewater phase was extracted with ether once and the organic phases werecombined and dried over Na₂SO₄. Purification by column chromatographywith hexane as eluent gave a yellow oil (780 mg, yield 37.6%). ¹H NMR(CDCl₃, 500 MHz) δ=7.48 (d, J=5.5 Hz, 2H), 7.47 (d, J=5.5 Hz, 2H), 3.20(t, J=7.5 Hz, 4H), 1.75-1.88 (m, 4H), 1.43-1.54 (m, 4H), 1.21-1.42 (bs,16H), 0.90 (t, J=7.0 Hz, 6H).

Step 2: Preparation of4,8-dioctyl-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of 4,8-dioctylbenzo[1,2-b:4,5-b′]dithiophene (782 mg, 1.89mmol) in dry tetrahydrofuran (36 mL) was added n-butyllithium (2.5 M inhexane, 1.66 mL, 4.15 mmol) at −78° C. After 1 hour, trimethyltinchloride (877 mg, 4.40 mmol) was added in one portion. The mixture wasstirred at room temperature for 2 hours, poured into water and extractedwith ether three times. The organic layer was washed with brine anddried over anhydrous MgSO₄. Upon evaporating the solvent, a pale yellowoil was obtained (1.03 g, yield 74%). Upon standing for one week, yellowcrystals emerged and were collected (413 mg, yield 29%). ¹H NMR (CDCl₃,500 MHz) δ=7.51 (s, 2H), 3.22 (t, J=8.0 Hz, 4H), 1.76-1.89 (m, 4H),1.45-1.54 (m, 4H), 1.22-1.45 (bs, 16H), 0.90 (t, J=7.0 Hz, 6H), 0.47 (s,18H).

Example 1c Preparation of4,8-bis(2-ethylhexyl)-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

Step 1: Preparation of4,8-bis(2-ethylhexyl)benzo[1,2-b:4,5-b′]dithiophene

To a 100 mL flask under nitrogen was added magnesium (656 mg, 27 mmol)and anhydrous THF (10 mL). The mixture was heated under reflux and2-ethylhexyl bromide (5.6 mL, mmol) was added dropwise. The reactionmixture was kept at refluxing temperatures until all magnesium wasconsumed. After cooling down,4,8-dihydrobenzo[1,2-b:4,5-b′]dithiophene-4,8-dione (1.1 g, 5.0 mmol)was added in one portion. After refluxing for 1 hour more, it was cooleddown again to room temperature. SnCl₂ solution (7.5 g in 19 mL 10% HCl)was slowly added dropwise and then the mixture was kept at 60° C. for 1hour. After cooling down, brine (11 mL) was added. The organic phase wasseparated and dried over Na₂SO₄. The residue after vacuum evaporationwas purified by column chromatography with hexane as eluent and gave apale yellow oil (910 mg, yield 43%). 1H NMR (CDCl₃, 500 MHz) δ=7.47 (d,J=6.0 Hz, 2H), 7.45 (d, J=6.0 Hz, 2H), 3.08-3.20 (m, 4H), 1.92-2.04 (m,2H), 1.13-1.49 (m, 16H), 0.91 (t, J=7.0 Hz, 6H), 0.85 (t, J=7.0 Hz, 6H).

Step 2: Preparation of4,8-bis(2-ethylhexyl)-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of 4,8-bis(2-ethylhexyl)benzo[1,2-b:4,5-b′]dithiophene(237 mg, 0.57 mmol) in dry tetrahydrofuran (11 mL) was addedn-butyllithium (2.5 M in hexane, 0.5 mL, 1.25 mmol) at −78° C. After 1hour, trimethyltin chloride (264 mg, 1.32 mmol) was added in oneportion. The mixture was stirred at room temperature for 2 hours, pouredinto water (20 mL) and extracted with ether three times. The organiclayer was washed with brine and dried over anhydrous MgSO₄. Uponevaporating the solvent, a pale yellow oil was obtained (437 mg, yield100%). Upon standing in a freezer for 2 days, pale yellow crystalsemerged and were collected (326 mg, yield 77%). 1H NMR (CDCl₃, 500 MHz)δ=7.51 (s, 2H), 3.07-3.23 (m, 4H), 1.96-2.07 (m, 2H), 1.21-1.50 (m,16H), 0.94 (t, J=7.0 Hz, 6H), 0.89 (t, J=7.0 Hz, 6H), 0.46 (s, 18H).

Example 1d Preparation of4,8-bis(10-phenyldecyl)-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

Step 1: Preparation of 10-bromodecylbenzene

To a 250 mL flask in ice-water bath was added 1,10-dibromodecane (46.0g, 153 mmol) and anhydrous THF (100 ml) under nitrogen. Phenyl lithium(1.8 M in dibutyl ether, 28.5 mL, 51 mmol) was added dropwise. Afteraddition was completed, the reaction mixture was stirred for 1 hour andwarmed to room temperature. After 48 hours, it was quenched with H₂O(200 mL), extracted with CH₂Cl₂ (200 mL×2) and dried. Afterconcentration, the residue was distilled to give a colorless oil (9.35g, yield 61.7%) at 130° C./0.07 mmHg. ¹H NMR (CDCl₃, 500 MHz)δ=7.27-7.32 (m, 2H), 7.20 (d, J=6.5 Hz, 3H), 3.43 (t, J=7.0 Hz, 2H),2.62 (t, J=8.0 Hz, 2H), 1.84-1.96 (m, 2H), 1.60-1.68 (m, 2H), 1.41-1.52(m, 2H), 1.24-1.41 (m, 10H).

Step 2: Preparation of4,8-bis(10-phenyldecyl)benzo[1,2-b:4,5-b′]dithiophene

To a 100 mL flask under nitrogen was added magnesium (486 mg, 20 mmol)and anhydrous THF (10 mL). The mixture was heated under reflux and10-bromodecylbenzene (5.95 g, 20 mmol) was added dropwise. The reactionmixture was kept under reflex temperatures until all magnesium wasconsumed. Subsequently,4,8-dihydrobenzo[1,2-b:4,5-b′]dithiophene-4,8-dione (1.1 g, 5.0 mmol)suspended in anhydrous THF (10 ml) was added dropwise. After refluxingfor 3 hours more, it was cooled down to room temperature. SnCl₂ solution(7.5 g in 19 mL 10% HCl) was slowly added dropwise and then the mixturewas kept at 60° C. overnight. After cooling down, brine (25 mL) wasadded. The organic phase was separated and dried over Na₂SO₄. Theresidue after vacuum evaporation was purified by column chromatographywith hexane/AcOEt 50:1 as eluent and gave a pale yellow oil (466 mg,yield 15%), which turned into a solid upon standing for a few days. ¹HNMR (CDCl₃, 500 MHz) δ=7.48 (d, J=6.0 Hz, 2H), 7.46 (d, J=5.0 Hz, 2H),7.27-7.32 (m, 4H), 7.19 (d, J=7.0 Hz, 6H), 3.19 (t, J=8.0 Hz, 4H), 2.61(t, J=7.5 Hz, 4H), 1.75-1.86 (m, 4H), 1.58-1.67 (m, 4H), 1.42-1.51 (m,4H), 1.15-1.41 (m, 20H).

Step 3: Preparation of4,8-bis(10-phenyldecyl)-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of 4,8-bis(10-phenyldecyl)benzo[1,2-b:4,5-b′]dithiophene(466 mg, 0.75 mmol) in dry tetrahydrofuran (15 mL) was addedn-butyllithium (2.5 M in hexane, 0.66 mL, 1.65 mmol) at −78° C. After 1hour, trimethyltin chloride (349 mg, 1.75 mmol) was added in oneportion. The mixture was stirred at room temperature overnight, pouredinto water (25 mL) and extracted with ether three times. The organiclayer was washed with brine and dried over anhydrous MgSO₄. Uponevaporating the solvent, a pale yellow oil was obtained (500 mg, yield70%). ¹H NMR (CDCl₃, 500 MHz) δ=7.49 (s, 2H), 7.27-7.32 (m, 4H), 7.17(d, J=7.5 Hz, 6H), 3.19 (t, J=7.5 Hz, 4H), 2.59 (t, J=8.0 Hz, 4H),1.75-1.84 (m, 4H), 1.56-1.66 (m, 4H), 1.42-1.50 (m, 4H), 1.17-1.41 (m,20H), 0.45 (s, 18H).

Example 1e Preparation of4,7-bis(5-bromo-4-dodecylthiophen-2-yl)-2,1,3-benzothiadiazole

Step 1: Preparation of 4,7-dibromo-2,1,3-benzothiadiazole

To a solution of benzothiadiazole (10 g, 73.44 mmol) in 150 mL of HBr(48%) was added dropwise a solution of Br₂ (35.21 g, 220.32 mmol) in 100mL of HBr (48%) very slowly. After refluxing for 6 hours, an orangesolid precipitated. The mixture was allowed to cool to room temperature,and a saturated solution of NaHSO₃ was added to neutralize the residualamount of Br₂. The mixture was filtered and washed exhaustively withwater. The solid was then washed once with cold diethyl ether andpurified by flash chromatography with CHCl₃ as eluent to give a paleyellow solid (18.4 g, yield 85%). ¹H NMR (CDCl₃, 500 MHz), δ=7.73 (s,2H).

Step 2: Preparation of4,7-bis(4-dodecylthiophen-2-yl)-2-yl)-2,1,3-benzothiadiazole

To a 100 mL round bottom flask under nitrogen,4,7-dibromo-2,1,3-benzothiadiazole (1.18 g, 4.0 mmol),2-trimethylstannyl-4-dodecylthiophene (4.03 g, 9.7 mmol, preparedaccording to Macromolecules 2002, 35, 6883), Pd₂ (dba)₃ (146.5 mg, 0.16mmol), tri(2-furyl)phosphine (148.6 mg, 0.64 mmol) and anhydrous THF (30mL) were added. The mixture was heated under reflux for 20 hours andallowed to cool down. The solvent was removed by rotary evaporator antedthe residue was purified by column chromatography with CHCl₃:hexane 1:3as eluent to give an orange solid (2.0 g, yield 78%). ¹H NMR (CDCl₃, 500MHz), δ=8.00 (s, 2H), 7.85 (s, 2H), 7.06 (s, 2H), 2.71 (t, J=7.5 Hz,4H), 1.68-1.76 (m, 4H), 1.19-1.47 (m, 36H), 0.90 (t, J=6.8 Hz, 6H).

Step 3: Preparation of4,7-bis(5-bromo-4-dodecylthiophen-2-yl)-2,1,3-benzothiadiazole

To a 50 mL round bottom flask wrapped with aluminum foil under nitrogen,4,7-bis(4-dodecylthiophen-2-yl)-2,1,3-benzothiadiazole (637 mg, 1.0mmol), NBS (392 mg, 2.2 mmol) and CHCl₃ (13 mL) were added. The mixturewas stirred overnight and the solvent was removed by rotary evaporator.The residue was purified by column chromatography with CHCl₃:hexane 1:50as eluent to give a red solid (520 mg, yield 65%). ¹H NMR (CDCl₃, 500MHz), δ=7.78 (s, 2H), 7.76 (s, 2H), 2.65 (t, J=7.8 Hz, 4H), 1.64-1.72(m, 4H), 1.21-1.47 (m, 36H), 0.89 (t, J=6.8 Hz, 6H).

Example 1f Preparation of4,7-bis(5-bromo-4-dodecyl-2-thienyl)-2,1,3-benzothiadiazole

The building block 4,7-bis(4-dodecyl-2-thienyl)-2,1,3-benzothiadiazolewas prepared according to literature procedures and dissolved inchloroform (60 mL). Acetic acid (20 mL) and N-bromosuccinimide (0.746 g,4.19 mmol) were added. The reaction was stirred at room temperatureovernight. Water (150 mL) was added and the mixture was extracted withchloroform. The organic layer was separated, washed with an saturatedaqueous solution of NaHCO₃, followed by water, and dried over MgSO₄.Solvent was removed under vacuum and the residue was purified bychromatography using a 1:4 mixture of dichloromethane/hexanes as eluent.The yield of the4,7-bis(5-bromo-4-dodecyl-2-thienyl)-2,1,3-benzothiadiazole was 1.46 g(88%). ¹H NMR (CDCl₃, 500 MHz) δ: 7.77 (s, 2H), 7.76 (s, 2H), 2.64 (t,J=7.8, 4H), 1.67 (m, 4H), 1.40-1.25 (m, 36H), 0.86 (t, J=7.5, 6H).

Example 1g Preparation of4,8-bis[(2-hexyldecyl)oxy]-benzo[1,2-b:4,5-b′]dithiophene

Benzo[1,2-b:4,5-b′]dithiophene-4,8-dione (1.0 g, 4.54 mmol) and Znpowder (0.659 g, 10.1 mmol) were suspended in ethanol (10 mL). Asolution of NaOH (3 g) in water (15 mL) was added. The resulting mixturewas heated to reflux for 1 hour, after which2-hexyldecyl(4-methylbenzenesulfonate) (3.86 g, 9.73 mmol) was added.The reaction was heated to reflux overnight. The reaction was cooled toroom temperature and water (50 mL) was added. The reaction was extractedwith ether, followed by separation and drying of the organic layer overMgSO₄. Solvent was removed and the residue was purified bychromatography (10% dichloromethane in hexanes as eluent). The yield ofthe 4,8-bis[(2-hexyldecyl)oxy]-benzo[1,2-b:4,5-b′]dithiophene was 0.80 g(26%). ¹H NMR (CDCl₃, 500 MHz) δ=7.47 (d, J=2.75, 2H), 7.36 (d, J=2.75,2H), 4.16 (m, 4H), 1.86 (m, 2H), 1.38-1.65 (m, 48H), 0.86 (m, 12H).

Example 1h Preparation of4,8-bis[(2-hexyldecyl)oxy]-2,6-bis(1,1,1-trimethyl-stannanyl)benzo[1,2-b:4,5-b′]dithiophene

4,8-Bis[(2-hexyldecyl)oxy]-benzo[1,2-b:4,5-b′]dithiophene (0.80 g, 1.19mmol) was dissolved in dry THF (10 mL) under nitrogen. The solution wascooled to −70° C. and butyllithium (1.0 mL, 2.M solution in hexanes, 2.5mmol) was added dropwise. The reaction was allowed to warm to roomtemperature over 2 hours and cooled back to −78° C. Trimethyltinchloride (0.61 g, 3.0 mmol) was added. The reaction was allowed to warmto room temperature and stirred under nitrogen overnight. Water (50 mL)was added and the reaction was extracted with ether. Organic layer wasseparated and dried over Na₂SO₄. Solvent was removed under vacuum. Tothe residue was added ethanol (10 mL) and the suspension was stirredovernight. The resulting white solids were collected by filtration anddried under vacuum to afford the product4,8-bis[(2-ethylhexyl)oxy]-2,6-bis(1,1,1-trimethyl-stannanyl)benzo[1,2-b:4,5-b′]dithiophene(0.58 g, 49%). ¹H NMR (CDCl₃, 500 MHz) δ=7.52 (m, 2H), 4.17 (d, J=5.0Hz, 4H), 1.86 (m, 2H), 1.67 (m, 4H), 1.28-1.55 (m, 44H), 0.86 (m, 12H),0.55 (m, 18H).

Example 2 Polymer Synthesis Example 2a Preparation ofpoly[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(3-dodecyl-2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(4-dodecyl-2,5-thiophenediyl)}-co-[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(2,5-thiophenediyl)}](x=0.77;y=0.23)

The building block 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole wasprepared according to literature procedures (Moule et al., Chem. Mater.,2008, 20: 4045-4050). To a Schlenk flask were added4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (46.23 mg, 0.101mmol),4,8-bis[(2-hexyldecyl)oxy]-2,6-bis(1,1,1-trimethyl-stannanyl)benzo[1,2-b:4,5-b′]dithiophene(141.65 mg, 0.135 mmol),4,7-bis(5-bromo-4-dodecyl-2-thienyl)-2,1,3-benzothiadiazole (24.6 mg,0.0309 mmol), Pa₂ dba₃ (4.93 mg, 0.00538 mmol), and P(o-tol)₃ (13.10 mg,0.431 mmol). The flask was degassed and backfilled with nitrogen threetimes. Dry chlorobenzene (20 mL) was injected and the reaction washeated to 130° C. for 18 hours. The reaction was cooled to roomtemperature and the content of the flask was poured into methanol (100mL). The precipitates were collected by filtration and the solids wereextracted with acetone for 1 hour, dichloromethane for 3 hours andchloroform for three hours. Finally the polymer was extracted withchlorobenzene. The chloroform solution was poured into methanol, and theprecipitates were again collected by filtration, dried under vacuum toafford the title polymer (40 mg).

Example 2b Preparation ofpoly[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(3-dodecyl-2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(4-dodecyl-2,5-thiophenediyl)}-co-[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(2,5-thiophenediyl)}](x=0.71;y=0.29)

To a Schlenk flask were added4,8-bis[(2-hexyldecyl)oxy]-2,6-bis(1,1,1-trimethyl-stannanyl)benzo[1,2-b:4,5-b′]dithiophene(129.74 mg, 0.123 mmol),4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (39.53 mg, 0.0863mmol), 4,7-bis(5-bromo-4-dodecyl-2-thienyl)-2,1,3-benzothiadiazole(27.43 mg, 0.345 mmol), Pa₂ dba₃ (4.513 mg, 0.000493 mmol), andP(o-tol)₃ (12.00 mg, 0.394 mmol). The flask was degassed and backfilledwith nitrogen three times. Dry chlorobenzene (20 mL) was injected andthe reaction was heated to 130° C. for 18 hours. The reaction was cooledto room temperature and the content of the flask was poured intomethanol (200 mL). The precipitates were collected by filtration and thesolids were extracted with ethyl acetate for 5 hours, and THF for 5hours. Finally the polymer was extracted with chlorobenzene. Thechloroform solution was poured into methanol, and the precipitates wereagain collected by filtration, dried under vacuum to afford the titlepolymer (64 mg, 49% yield).

Example 2c Preparation ofpoly[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(3-dodecyl-2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(4-dodecyl-2,5-thiophenediyl)-co-[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(2,5-thiophenediyl)}](x=0.62;y=0.38)

To a Schlenk flask were added4,8-bis[(2-hexyldecyl)oxy]-2,6-bis(1,1,1-trimethyl-stannanyl)benzo[1,2-b:4,5-b′]dithiophene(117.27 mg, 0.111 mmol),4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (30.62 mg, 0.0668mmol), 4,7-bis(5-bromo-4-dodecyl-2-thienyl)-2,1,3-benzothiadiazole(33.64 mg, 0.0423 mmol), Pa₂ dba₃ (4.08 mg, 0.0045 mmol), and P(o-tol)₃(10.85 mg, 0.0356 mmol). The flask was degassed and backfilled withnitrogen three times. Dry chlorobenzene (20 mL) was injected and thereaction was heated to 130° C. for 18 hours. The reaction was cooled toroom temperature and the content of the flask was poured into methanol(100 mL). The precipitates were collected by filtration and the solidswere extracted with methanol for 8 hours, ethyl acetate for 5 hours, andthen dichloromethane for 15 hours. Finally the polymer was extractedinto chloroform. The chloroform solution was poured into methanol, andthe precipitates were again collected by filtration, dried under vacuumto afford the title polymer 88 mg (72% yield).

Example 2d Preparation ofpoly[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(3-dodecyl-2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(4-dodecyl-2,5-thiophenediyl)-co-[{2,6-bis[(2-hexyldecyl)oxy]benzo[1,2-b:4,5-b′]dithiophene)(2,5-thiophenediyl)-2,1,3-benzothiadiazole-4,7-diyl(2,5-thiophenediyl)}](x=0.5;y=0.5)

To a Schlenk flask were added4,8-bis[(2-hexyldecyl)oxy]-2,6-bis(1,1,1-trimethyl-stannanyl)benzo[1,2-b:4,5-b′]dithiophene(600 mg, 0.60 mmol), 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole(137.9 mg, 0.301 mmol),4,7-bis(5-bromo-4-dodecyl-2-thienyl)-2,1,3-benzothiadiazole (229.60 mg,0.289 mmol), Pa₂ dba₃ (22.05 mg, 0.024 mmol), and P(o-tol)₃ (58.63 mg,0.193 mmol). The flask was degassed and backfilled with argon threetimes. Dry chlorobenzene (90 mL) was injected and the reaction washeated to 130° C. for 18 hours. The reaction was cooled to roomtemperature and the content of the flask was poured into methanol (200mL). The precipitates were collected by filtration and the solids wereextracted with methanol for 5 hours, ethyl acetate for 5 hours, hexanesfor 15 hours, and then dichloromethane for 5 hours. Finally the polymerwas extracted into chloroform. The chloroform solution was poured intomethanol, and the precipitates were again collected by filtration, driedunder vacuum to afford the title polymer 511 mg (75% yield).

Example 3 Characterization of Polymers Example 3a Optical properties

Optical absorption measurements of polymers from Example 2 were carriedout using a Cary UV-vis spectrometer on chloroform solution of thepolymer. The onset of the absorption is used to estimate the polymerbandgap.

Example 3b Electronic Properties

Cyclic voltammetry measurements of polymers from Example 2 were carriedout under nitrogen atmosphere using a BAS-CV-50W voltammetric analyzerwith 0.1M tetra-n-butylammonium hexafluorophosphate in actonitrile asthe supporting electrolyte. A platinum disk working electrode, aplatinum wire counter electrode and a silver wire reference electrodewere employed and Fc/Fc⁺ was used as reference for all measurements. Thescan rate was 50 mV/S. Polymer films were produced by drop casting from0.2% (w/w) toluene solutions. The supporting electrolyte solution wasthoroughly purged with N₂ before all CV measurements.

Using data from the cyclic voltammograms, the HOMO of a representativecopolymer from Example 2 was calculated from the equation4.44-1.06=−5.50; and the LUMO was calculated from the equation−4.44−1.07=−3.37.

Example 4 Device Fabrication Example 4a Thin Film Transistor Fabricationand Measurements

Charge carrier mobilities of the polymers were determined using organicfield effect transistors. Bottom-gate TFTs were fabricated on Si/SiO₂substrates, the surface of which was modified with a monolayer of OTSbefore semiconductor deposition. Semiconductors were spun from pristinepolymer solution (10 mg/ml in dichlorobenzene by volume) onto thesesubstrates and the films were dried in a vacuum oven overnight. Autop-contacts (30 nm) were thermally evaporated through metal stencilsonto these films at a vacuum of 1×10⁻⁶ torr to complete the device. Thechannel dimensions of the devices are about 25 μm (length) and about 500μm (width). The capacitance of the dielectric is 10 nF/cm². The deviceswere characterized in air and in an electrically shielded environment(Signatone dark box). Three Signatone probes were used to access theelectrodes, and the signals were triaxially-shielded from very near theprobe tip to a Keithley 4200 semiconductor characterization (3independent SMUs each equipped with a remote preamplifier). FET metrics(mobility, threshold voltage, and on/off ratio) were extracted fromtransfer and output plots according to standard transistor equations.

FIG. 2 shows a representative transfer plot of a bottom-gate TFT using apolymer from Example 2 as the active layer. The extracted hole mobilityis about 8.2×10⁻³ cm²/Vs, and the current on/off ratio is about 1.5×10⁵.

Example 4b Photovoltaic Cell Fabrication and Measurements

Photovoltaic devices incorporating the copolymers described in Example 2were fabricated and characterized. Devices with both thin (˜100 nm) andthick (˜250 nm) active layer were built. Before device fabrication, thepatterned ITO-coated glass substrates were cleaned by ultrasonictreatment in detergent, de-ionized water, acetone, and isopropyl alcoholsequentially, followed by UV-ozone treatment for 40 minutes. A PEDOT:PSSlayer of about 40 nm thickness was spin-coated from an aqueous solution(HC Stark, Baytron AI 4083) onto ITO coated glass substrates, followedby baking at 150° C. for 30 minutes in air. The polymer/fullerenemixture solutions in 1,2-dichlorobenzene were prepared at the followingratios: polymer:C₆₀PCBM 12:24 mg/ml and polymer:C₇₀PCBM 12:18 mg/ml. Themixture solutions were then stirred for at least 1 hour at 120° C. in aglove box and were cooled down to ˜60° C. before spin-coating on top ofthe PEDOT:PSS layer. To complete the device fabrication, a layer oflithium fluoride (LiF) having a thickness of about 0.6 nm and analuminum layer of about 100 nm thickness were successively depositedthermally under vacuum of ˜10⁻⁶ Torr. The active area of the device wasabout 0.093 cm². The devices were then encapsulated with a cover glassusing EPO-TEK OG112-6 UV curable epoxy (Epoxy Technology) in the glovebox.

The photovoltaic characteristics of the encapsulated devices were testedin air. The current density-voltage (J-V) curves were obtained using aKeithley 2400 source-measure unit. The photocurrent was measured undersimulated AM1.5G irradiation (100 mW cm⁻²) using a xenon-lamp-basedsolar simulator (Newport 91160A 300 W Class-A Solar Simulator, 2 inch by2 inch uniform beam) with air mass 1.5 global filter. The lightintensity was set using a NREL calibrated silicon photodiode with acolor filter. External quantum efficiency was measured using Newport'sQE setup. Incident light from a xenon lamp (300 W) passing through amonochromator (Newport, Cornerstone 260) was focused on the active areaof the cell. The output current was measured using a currentpre-amplifier (Newport, 70710QE) and a lock-in amplifier (Newport, 70105dual channel Merlin). A calibrated silicon diode (Newport 70356) wasused as a reference.

Typical JV characteristics are shown in FIG. 3. The device efficiencieswere corrected for mismatch between the solar simulator and the AM1.5Gusing the EQE spectra shown in FIG. 4. A summary of the devicecharacteristics is given in Table 2 below.

TABLE 2 Device characteristics for random copolymer-based OPV devices.V_(oc) (V) J_(sc) (mA/cm²) FF (%) PCE (%) Polymer:C₆₀PCBM thin 0.74 8.8575.9 4.97 Polymer:C₆₀PCBM thick 0.74 11.76 71.3 6.20 Polymer:C₇₀PCBMthin 0.76 11.23 72.7 6.20 Polymer:C₇₀PCBM thick 0.74 13.19 70.3 6.86

Comparative Examples Comparative Example 1 Preparation ofpoly[{2,6-(4,8-dioctylbenzo[1,2-b:4,5-b′]dithiophene)}-alt-{5,5-(4,7-bis(4′-dodecylthien-2′-yl)-2,1,3-benzothiadiazole)}](SL15)

To a 100 mL storage vessel,4,8-bis(2-ethylhexyl)-2,6-bis-trimethylstannylbenzo[1,2-b:4,5-b′]dithiophene (55.5 mg, 75 mmol),4,7-bis(5-bromo-4-dodecylthiophen-2-yl)-2,1,3-benzothiadiazole (59.6 mg,75 μmol), Pd₂ (dba)₃ (2.7 mg, 4 mol %) and tri(o-tolyl)phosphine (3.7mg, 16 mol %) were added and mixed in anhydrous chlorobenzene (10 mL)under argon and stirred at 133° C. for 72 hours. After cooling to roomtemperature, the reaction mixture was poured into MeOH (50 mL), filteredand dried under vacuum oven to give a black solid (78.5 mg, crude yield100%). Elemental Analysis: Calcd. C, 73.37; H, 8.66; N, 2.67; Found: C,72.25, H, 8.09, N, 2.97.

Comparative Example 2 Fabrication of an OPV Device Based on SL15

Photovoltaic devices were fabricated incorporating SL15 and bucky ballcompounds such as PCBM. Before device fabrication, patterned ITO-coatedglass substrates were cleaned by ultrasonic treatment in detergent,de-ionized water, acetone, isopropyl alcohol sequentially, and UV-ozonetreatment for 15 minutes. A PEDOT:PSS layer of about 40 nm thickness wasspin-coated from an aqueous solution onto ITO-coated glass substrates,followed by baking at 150° C. for 30 minutes in the air. Thepolymer/PCBM mixture solution in chlorinated solvents (such aschloroform) was prepared at a concentration of 5:10 mg/ml. The solutionwas then stirred for 2 hours at 40° C. in a glove box and wasspin-coated on top of the PEDOT:PSS layer. The thickness of active layerwas about 100-300 nm. To complete the device fabrication, a thin layerof lithium fluoride (LiF) and 100 nm thickness of aluminum weresuccessively deposited thermally under vacuum of ˜10⁻⁶ Torr. The activearea of the device was about 0.088 cm². The devices were thenencapsulated with a cover glass using a UV curable epoxy in the glovebox.

Such devices using SL15 exhibit much poorer performance than devicesbased on polymers according to the present teachings, i.e., the polymersof formulae I, II, III, IV, and V. Specifically, devices using SL15demonstrated an average power conversion efficiency ˜2.2%, and a fillfactor ˜43%, both of which are significantly lower than the valuesreported in Example 4b in connection with the polymers according to thepresent teachings.

The present teachings encompass embodiments in other specific formswithout departing from the spirit or essential characteristics thereof.The foregoing embodiments are therefore to be considered in all respectsillustrative rather than limiting on the present teachings describedherein. Scope of the present invention is thus indicated by the appendedclaims rather than by the foregoing description, and all changes thatcome within the meaning and range of equivalency of the claims areintended to be embraced therein.

1. An electronic, optical or optoelectronic device comprising: a firstelectrode, a second electrode, and a semiconductor component disposedbetween the first electrode and the second electrode, the semiconductorcomponent comprising a random copolymer having the formula:

wherein M is an optionally substituted 2,1,3-benzothiadiazole-4,7-diylgroup; each of R¹ and R² is an organic group comprising a cyclic moiety;R⁷ is a linear C₆₋₂₀ alkyl group or a linear C₆₋₂₀ alkoxy group; and xand y are real numbers representing mole fractions, wherein 0.1≦x≦0.9,0.1≦y≦0.9, and the sum of x and y is about
 1. 2. The device of claim 1,wherein the random copolymer has the formula:

wherein M, R¹, R², R⁷, x and y are as defined in claim
 1. 3. The deviceof claim 1, wherein M is

wherein R⁵ and R⁶ independently are H or -L-R, wherein L, at eachoccurrence, independently is selected from the group consisting of O, S,and a covalent bond; and R, at each occurrence, independently is a C₁₋₄₀alkyl group.
 4. The device of claim 1, wherein

wherein p is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or
 10. 5. The device of claim1, wherein 0.2≦x≦0.8, 0.2≦y≦0.8, and the sum of x and y is about
 1. 6.The device of claim 1, wherein 0.3≦x≦0.7, 0.3≦y≦0.7, and the sum of xand y is about
 1. 7. The device of claim 1, wherein the random copolymerhas a degree of polymerization (n) in the range from 10 to about 10,000.8. The device of claim 1 configured as an organic photovoltaic devicecomprising an anode, a cathode, and in between the anode and the cathodethe semiconductor component according to claim
 1. 9. The device of claim8, wherein the organic photovoltaic device is a bulk heterojunctionphotovoltaic device.
 10. The device of claim 9, wherein thesemiconductor component is photoactive and comprises a blend material,wherein the copolymer in the blend material functions as anelectron-donor and the blend material further comprises anelectron-acceptor compound.
 11. The device of claim 10, wherein theelectron-acceptor compound is a fullerene compound.
 12. The device ofclaim 11, wherein the fullerene compound is [6,6]-phenyl-C₆₁-butyricacid methyl ester (PCBM).
 13. The device of claim 11, wherein thefullerene compound is C₇₀PCBM.
 14. The device of claim 8, wherein thepower conversion efficiency is at least about 4%.
 15. The device ofclaim 8, wherein the power conversion efficiency is at least about 5%.16. The device of claim 8, wherein the power conversion efficiency is atleast about 6%.
 17. The device of claim 1 configured as an organic lightemitting diode comprising a substrate, an anode, a cathode, and inbetween the anode and the cathode the semiconductor component accordingto claim
 1. 18. The device of claim 1 configured as an organictransistor further comprising a third electrode and a dielectriccomponent, wherein the semiconductor component is in contact with thefirst electrode and the third electrode, and the dielectric component isin contact with the semiconductor component on one side and the secondelectrode on an opposite side.
 19. The device of claim 18, wherein theorganic transistor is an organic thin film transistor.
 20. The device ofclaim 18, wherein the organic transistor is an organic light emittingtransistor.